Whereas the preceding parable of the vine wood emphasized unfruitfulness, in this chapter the allegory of a wife emphasizes unfaithfulness.  Believers today as the bride of Christ are to be both fruitful and faithful for as Paul instructed the Romans

my brethren, you also were made to die to the Law through the body of Christ, that you might be joined to (KJV/NKJV = married to) another, to Him who was raised from the dead, (in order) that we might bear fruit for God. (which fulfills our purpose for true spiritual fruit brings glory to God) (see note Romans 7:4)

Paul goes on to explain that before we were born again,

while we were in the flesh, the sinful passions, which were aroused by the Law, were at work in the members of our body to bear fruit for death. But now we have been released from the Law, having died to that by which we were bound, so that we serve in newness of the Spirit (the only way to bear the fruit of the Spirit!) and not in oldness of the letter. (see notes Romans 7:5; 7:6)

Wesley's plea was

Lord, let me not live to be useless.

This is the longest chapter in Ezekiel and closely parallels the indictment of Judah in Ezekiel 23 (2 sisters). In this chapter God describes Israel’s sin and unfaithfulness to His love in such frank and indicting terms that some of the ancient rabbis refused to allow public reading of these passages verses! Expositor's adds

make known  to Jerusalem her abominations (Ezekiel 20:4; 22:2; 23:36; 33:7-9; Ho 8:1)

The KJV translates it more "forcefully" as cause Jerusalem to know.

NET Bible translates it as confront Jerusalem.

The English translation of the Septuagint (LXX)(Greek translation of the Hebrew) has "testify to Jerusalem" where the Greek word for testify is diamarturomai which means to solemnly witness or bear witness This is an interesting opening because Ezekiel is in exile in Babylon and not in Jerusalem. One explanation is that although Jerusalem does refer to the city, in context the term is being used also in a "broader" sense as representative of the Jewish people. 

The Amplified Version translates it with this thought (verse 2) as "Jerusalem [representing Israel]".

Ezekiel was to give an uncompromising message, and like Isaiah was to

Cry loudly, do not hold back. Raise your voice like a trumpet, and declare to (God's) people their transgression and to the house of Jacob their sins. (Isa 58:1)

As God told Hosea, Ezekiel was to

Put the trumpet to your lips! Like an eagle the enemy comes against the house of the LORD (in the context of Hosea that enemy was Assyria, and for Ezekiel of course was Babylon), because they have transgressed (broken, rejected) My covenant, and rebelled against My law.

Quoting the NLT of Isaiah 57:12

Now I will expose your so-called good deeds that you consider so righteous. None of them will benefit or save you.

This allegory of Jerusalem serves to expose her so-called good deeds and should also serve as a dramatic warning to anyone who says they are saved and yet continues to live in their "abominations", for

by this the children of God and the children of the devil are obvious: anyone who does not practice righteousness is not of God, nor the one who does not love his brother. (1Jn 3:10)

Abominations (tow'ebah) ("loathsome practices" NJB, "loathsome sins" NLT; "detestable practices" NIV) refers to that which causes one to disgust, abhor, loathe or detest and in context the one who abhors Jerusalem's ("Israel's") conduct is God. One of the most striking, sad and powerful examples of their abominations is found in Ezekiel 8 where God had instructed His prophet to

"Go in and see the wicked abominations that they are committing (in the Holy Temple)....every form of creeping things and beasts and detestable things, with all the idols of the house of Israel, were carved on the wall (of the Temple area) all around. And standing in front of them were seventy elders of the house of Israel...each man with his censer in his hand, and the fragrance of the cloud of incense rising...the elders of the house of Israel...in the dark, each man in the room of his carved images" totally deceived saying "The LORD does not see us; the LORD has forsaken the land." God went on to tell Ezekiel that he would "see still greater abominations which they are committing...(at) the entrance of the gate of the LORD'S house which was toward the north... women...sitting there weeping for Tammuz." But God was not finished with this horrid picture, declaring to Ezekiel that he would "see still greater abominations than these... and behold, at the entrance to the temple of the LORD, between the porch and the altar, were about 25 men with their backs to the temple of the LORD and their faces toward the east; and they were prostrating themselves eastward toward the sun." (backs to the Creator, bowing to the creation as "sun worshippers"!) (Ezekiel 8:9-17)

This Hebrew word (tow'ebah) is used to describe a variety of specific "abominations" including

idolatry (Dt 7:25)

human sacrifice (Dt 12:31),

engaging in occult activities (Dt 18:9-14),

conducting one's business dishonestly (Dt 25:13-16),

practicing ritual prostitution (1Ki 14:23ff),

and similar acts of disobedience (Pr 6:16-19 lists seven abominations).

Jerusalem was guilty of practicing all of these abominations, any one of which would have been enough to justify God's wrath on them. It is also notable that on occasion this Hebrew word translated abominations (tow'ebah) is also used as a synonym for "idol" (eg, Isa 44:19) or even for specific pagan false gods, for example, referring to the idol Milcom as

"the abomination of the Ammonites" (in 2Ki 23:13)

At the other end of the spectrum,

he who turns away his ear from listening to the law, even his prayer is an abomination" (Pr 28:9).

And so in Isaiah God says to Israel

Lord God - NIV more accurately translates it sovereign LORD

God had appointed (Ezekiel) a watchman for the house of Israel" and so when he head a message from (God's) mouth" he would "give them warning" (Ezek 33:7)

The IVP Bible background commentary has a well reasoned comment stating that

This passage operates on two levels. First, it is correct to tie Jerusalem, at least the Jebusite city, to Amorite and North Syrian Hittite political origins. This is established by its mention in the El Amarna texts. However, on a symbolic level, in confronting Jerusalem with its mixed ancestry (tying it to three of the seven major inhabitant groups of Canaan listed in Ex 3:8), God identifies the place and the people as utterly corrupt. When the land was conquered, it was the responsibility of the Israelites to purify it of its idolatrous traditions (Dt 7:1–5), but instead the people became just like the nations they were supposed to displace. (Matthews, V. H., et al, The IVP Bible Background Commentary: Old Testament. Downers Grove, IL: InterVarsity Press)

Your origin and your birth are from the land of the Canaanite(Ezekiel 16:45; 21:30; Ge 11:25,29; Joshua 24:14; Neh 9:7; Isa 1:10; 51:1,2; Mt 3:7; 11:24; Lu 3:7; Jn 8:44; Eph 2:3; 1Jn 3:10)

Origin - ancestry, parentage, lineage, family line with a focus on the origin

Birth - family, relatives, kindred

The land of the Canaanite - The physical location of Jerusalem is in the "land of Canaan", but as noted above, God is also alluding to the moral condition of Jerusalem.

your father was an Amorite and your mother a Hittite

The Amorites elsewhere is Scripture were used by God to represent the epitome of evil, in Genesis God declaring that

in the fourth generation (Abraham's offspring) shall return here (to Canaan), for the iniquity of the Amorite is not yet complete. (Ge 15:16)

Was Jerusalem's "father" literally an Amorite and her "mother" literally a Hittite? In Isaiah God declares to his people (once in this same chapter identifying them as synonymous with Jerusalem, see Isa 51:17)

Listen to me, you who pursue righteousness, who seek the LORD: Look to the rock from which you were hewn, and to the quarry from which you were dug. Look to Abraham your father, and to Sarah who gave birth to you in pain, when he was one I called him, then I blessed him and multiplied him. (Isa 51:1-2)

This verse begs the question -- What then is God saying with this description of Jerusalem?

I agree with Morris' comment, where he notes that

Both Amorites and Hittites were prominent in Canaan when Abraham arrived there from Ur of the Chaldees. Neither Abraham, Sarah, Rebecca, Rachel, nor Leah had any Amorite or Hittite blood in their personal heritage, but these pagan influences had infiltrated Jerusalem long before David captured it, and such influences had infected the children of Israel as soon as they returned there from Egypt under Joshua. (Morris, Henry: Defenders Study Bible. World Publishing)

And I would add that these pagan influences came into "full bloom" after Joshua died (see the detailed discussion below).

Mother a Hittite - see related note Ezekiel 16:44. 

Ryrie agrees with this interpretation commenting that this verse refers to

Jerusalem's moral genealogy included the Amorite (Canaanite) and Hittite (a non-Semitic pagan people). (The Ryrie Study Bible: New American Standard Translation: 1995. Moody Publishers)

John MacArthur agrees noting that

These names (Canaanite...Amorite...Hittite) identify the residents of Canaan who occupied the land when Abraham migrated there (cf. Ge 12:5,6). Jerusalem had the same moral character as the rest of Canaan." (MacArthur, J.: The MacArthur Study Bible Nashville: Word or Logos)

In preparation for entering the promised land, Moses had given Israel clear instructions that

When the LORD your God shall bring you into the land where you are entering to possess it, and shall clear away many nations before you, the Hittites and the Girgashites and the Amorites and the Canaanites and the Perizzites and the Hivites  and the Jebusites, seven nations greater and stronger than you, and when the LORD your God shall deliver (give) them before you, and you shall defeat (strike severely, slay, smite) them, then you shall utterly destroy them. You shall make no covenant with them and show no favor (no mercy) to them. Furthermore, you shall not intermarry with them; you shall not give your daughters to their sons, nor shall you take their daughters for your sons.  For they will turn your sons away from following Me to serve other gods; then the anger of the LORD will be kindled against you, and He will quickly destroy you. But thus you shall do to them: you shall tear down their altars, and smash their sacred pillars, and hew down their Asherim, and burn their graven images with fire. (Why?) For you are a holy (separated, set apart) people to the LORD your God; the LORD your God has chosen you to be a people for His own possession (treasured possession) out of all the peoples who are on the face of the earth. For you are a holy people to the LORD your God; the LORD your God has chosen you to be a people for His own possession out of all the peoples who are on the face of the earth.  The LORD did not set His love on you nor choose you because you were more in number than any of the peoples, for you were the fewest of all peoples, but because the LORD loved you and kept the oath which He swore to your forefathers, the LORD brought you out by a mighty hand, and redeemed you from the house of slavery, from the hand of Pharaoh king of Egypt." (Dt 7:1–8)

Moses specifically declared that

The graven images of their gods you are to burn with fire; you shall not covet the silver or the gold that is on them, nor take it for yourselves, lest you be snared by it, for it is an abomination to the LORD your God. And you shall not bring an abomination into your house, and like it come under the ban; you shall utterly detest it and you shall utterly abhor it, for it is something banned." (Dt 7:25-26)

Israel conquered Canaan under the leadership of Joshua and generally obeyed the Lord's command but after Joshua died Judges records that the tribes of Israel did not "drive out the Canaanites" (see note Judges 1:29) and that "the Canaanites lived among (in the midst of) them" (see note Judges 1:30)

Judges records that

the people served the LORD all the days of Joshua, and all the days of the elders who survived Joshua, who had seen all the great work of the LORD which He had done for Israel." (see notes Judges 2:7)

After Joshua and all of his generation had died

there arose another generation after them who did not know the LORD, nor yet the work which He had done for Israel. Then the sons of Israel did evil in the sight of the LORD, and served the Baals, and they forsook the LORD, the God of their fathers, who had brought them out of the land of Egypt, and followed other gods from among the gods of the peoples who were around them, and bowed themselves down to them; thus they provoked the LORD to anger. So they forsook the LORD and served Baal and the Ashtaroth." (see notes Judges 2:10-13)

Perhaps the sad story of Israel's being chosen by God and then choosing to reject His love and His Law can be summed up in the words of the Psalmist who records

Then (after the Red Sea deliverance) they believed His words. They sang His praise. They quickly forgot His works. They did not wait for His counsel. But craved intensely in the wilderness, and tempted God in the desert." (Ps 106:12-14)

They believed His words but soon forgot His works and pursued their will not God's. Ezekiel 16 is a summary in story (allegory) form of Israel's forgetting and forsaking, and should serve as an example for all of us regarding the importance of remembering God's love in choosing us and His works of grace and mercy in all of our lives.

Although I feel the context favors the above interpretation, in fairness one should be aware that some respected commentaries like Expositor's Bible Commentary interpret this passage more as a physical birth of the city of Jerusalem without any spiritual implications. Thus Expositors comments that

As for your birth, on the day you were born (Ezek 20:8,13; Ge 15:13; Ex 1:11-14; 2:23,24; 5:16-21; Dt 5:6; 15:15; Josh 24:2; Neh 9:7-9; Hos 2:3; Acts 7:6,7)

Ezekiel describes the procedures and treatment that would ordinarily be administered by the attendant at any normal newborn delivery (and which is still the practice of modern oriental midwives). The attendant (midwife) would cut and tie off the umbilical cord, rinse the blood of birth (most of which originates from the placenta separating from the uterus) from the newborn, clean the skin with salt water and wrap it in a blanket. The child would then normally be presented to the parents to be named. The clear implication in God's description of Jerusalem's birth is that she had no one to carry out the expected and necessary birth procedures. In other words Jerusalem was born in a helpless state.

your navel cord was not cut - Referring to not being cut from it's attachment to the placenta. Clearly this is one of the first maneuvers carried out for any newborn given proper attention. God is almost speaking in hyperbole here to exaggerate the effect that Jerusalem's birth without His rescuing hand would not have been a reality.

nor were you washed with water for cleansing (La 2:20; La 2:22; Lu 2:7,12)

you were not rubbed with salt Rubbing the skin with salt was supposed to make it firm and clean. Some feel this practice had antiseptic purposes.

Net Bible Note states that...

Arab midwives still cut the umbilical cords of infants and then proceed to apply salt and oil to their bodies.

even wrapped in cloths ("nor wrapped in swaddling cloths" ESV, "nor swaddled at all" KJV)

Nelson's New Illustrated Bible Dictionary describes the cloth with which newborns were wrapped as a

swaddling band (which) was a long, narrow strip of cloth used to wrap a newborn baby. To swaddle a child was to wrap an infant in strips of cloth, much like narrow bandages. This was believed to ensure the correct early development of the limbs. Thus, swaddling was a mark of parental love and care, while the need for swaddling symbolized the humble, dependent position of the newborn child...Although she could offer Jesus no better crib than an animals manger, Mary showed her mothers love by wrapping her baby in swaddling clothes (Luke 2:7, 12). The baby Jesus in swaddling bands reminds us of the great humility of our Lord in becoming a human being for our sakes." (Youngblood, R. F., Bruce, F. F., Harrison, R. K., & Thomas Nelson Publishers. Nelson's New Illustrated Bible Dictionary)

The International Standard Bible Encyclopedia (1915 edition) adds that

The oriental swaddling-clothes consist of a square of cloth and two or more bandages. The child is laid on the cloth diagonally and the corners are folded over the feet and body and under the head, the bandages then being tied so as to hold the cloth in position. This device forms the clothing of the child until it is about a year old, and its omission (Ezek 16:4) would be a token that the child had been abandoned. (Orr, J, et al: The International Standard Bible Encyclopedia: 1915)

Believer's Study Bible adds that

No eye looked with pity on you to do any of these things (the "things" in v4) for you (Ezekiel 2:6; Isa 49:15; La 2:11,19; 4:3,10)

The Hebrew word for pity (02347) (chuwc/chus) literally means to cover and figuratively to be compassionate, take pity, show mercy, the focus being on sparing or delivering one from great punishment. It conveys the basic meaning of to look with pity and often has the added nuance of a feeling which goes out toward one who is in trouble.

to have compassion on you - This is not the usual word translated compassion (racham) but is the Hebrew word here (02550) (chamal) connotes the emotional response which results or may result in an action to remove the recipient from impending difficulty. Chamal refers to the emotion leading one to spare another or have pity on them.

In context this point is a reminder to  Jerusalem that only God pitied and had compassion on her as on a baby, saving her from certain destruction, similar to what God did for the baby Moses who was placed in a basket in the Nile (same word chamal is used in Ex 2:6).

Net Bible adds that...

These verbs, “pity” and “spare,” echo the judgment oracles in Ezekiel 5:11; 7:4, 9; 8:18; 9:5, 10.

you were thrown out into the open field (Ge 21:10; Ex 1:22; Nu 19:16; Jer 9:21,22; 22:19)

Open - literally "the face of"

This phrase describes "infanticide" which was a widespread custom in the ancient near east used to eliminate unwanted children.

Moses records this same thought in a parallel passage...

He (God) found him (Israel) in a desert land, and in the howling waste of a wilderness; He encircled him, He cared for him, He guarded him as the pupil of His eye. (Deut 32:10) (Comment: God found Israel in a barren, desert land with no one to care for her and called Israel to be His own chosen people. His blessings came to the nation in a remarkable and unlimited way. He was patient with His people. When everyone else abandoned her, God still cared for Israel and provided for her. He had a father's undying love for his children. His love for His people does not mean that He is blind to their sins when they turn aside from Him. Nor does God's love mean that He never brings suffering to His people. The love of God means that God must chastise His people, on occasion, because He loves them. When God's love is expressed in wrath or judgment, it is wrath from a broken heart of love and with a purpose of bringing His people to obedience and maturity. Disciple's Study Bible)

The IVP Bible background commentary adds the historical note that there is

graphic evidence of (infanticide) from the Roman-Byzantine period... found in recent excavations at Ashkelon, where the remains of a hundred infants who had been disposed of in a sewer drain were uncovered. Infanticide was usually employed to get rid of female or malformed children. This was done as a means of either population control or economic necessity, since many villages were barely able to feed and care for healthy children and adults. The fact that the infant’s parents “cast it out” into a field has legal implications as well. They are renouncing all legal claims to the child and leaving it up to God and/or another person to “adopt” and thus save the child’s life. (Matthews, V. H., et al The IVP Bible background commentary : Old Testament  Downers Grove, IL: InterVarsity Press)

you were abhorred on the day you were born

When I passed by you and saw you squirming in your blood...I said...Live! (Ex 2:24,25; 3:7,8; Acts 7:34) (Isa 14:19; 51:23; Mic 7:10; Mt 5:13; Heb10:29; Rev 14:20) (20:5-10; Ex 19:4-6; Dt 9:4; Ps 105:10-15,26-37; Jn 5:25; Ro 9:15; Ep 2:4,5; Titus 3:3-7)

The Greek Septuagint (and the KJV) translation helps one understand that "in your blood" refers to pollution or defilement ("saw thee polluted in thy blood").

I made you numerous like plants of the field (Ge 22:17; Ex 1:7; 12:37; Acts 7:17)

 Again showing God's undeserved amazing grace.

Then you grew up, became tall, and reached the age for fine ornaments (10-13,16; Ex 3:22; Dt 1:10; 4:8; 32:10-14; 33:26-29; Ne9:18-25; Ps135:4; 147:20; 148:14; 149:2-4; Is 61:10; 62:3)

Here Jerusalem is described as a young woman who had reached marriageable age.

your breasts were formed and your hair had grown

Amplified: Now I passed by you again and looked upon you; behold, you were maturing and at the time for love, and I spread My skirt over you and covered your nakedness. Yes, I plighted My troth to you and entered into a covenant with you, says the Lord, and you became Mine.