FOR GROUND THAT DRINKS THE RAIN WHICH OFTEN FALLS ON IT: ge gar e piousa (AAPFSN) ton ep autes erchomenon (PMPMSA): (Deut 28:11,12 Ps 65:9-13, Ps 104:11-13 Isaiah 55:10-13 Joel 2:21-26 James 5:7)

To review remember that there are 4 Interpretative Views of Hebrews 6:4-8...

1). Saved, but lose salvation thru deliberate apostasy:

The Whole Counsel of God refutes the idea that one can lose his salvation. (Read passages like Jn 10:27-30; see notes on following passages Romans 8:35; 8:36; 8:37; 8:39; Ephesians 1:13, 1:14; Ephesians 4:30; Philippians 1:6; Hebrews 10:14; 1 Peter 1:3; 1:4; 1:5.)

2). Professors but not truly saved.

They clearly see the Truth ("enlightened"), experience the power to a degree ("tasted the good word of God and the powers of the age to come"), like Judas Iscariot (Mt 10:1-8) but they are like the rocky soil (see Lk 8:13), soil with thorns (Lk 8:14), who for a time conform to truth but in face of persecution (Lk 8:13), utterly and completely renounce the faith, falling away to perdition (Hebrews 3:12 see note, Hebrews 10:39 -note, Jn 17:12) (cf. Bruce, The Epistle to the Hebrews, pp. 118-125).

3). Saved persons who have fallen beyond repentance:

Falling into sin so that they are at the point of divine chastisement, having gone so far they cannot repent again of their sin. That they lose all their rewards.

4). Hypothetical case:

The proponents of this view feel that writer is presenting this hypothetical example to illustrate the folly of apostasy.

Ground that drinks the rain - The contrasting issue is either usefulness or worthlessness. The initial advantage described is the same and it is only the final result that is different. Agricultural illustrations are frequent in Scripture (Isaiah 5:1-7 [Israel compared to a vineyard cultivated by God and yet did not yield fruit] ; Isaiah 28:23-29; Ezek 19:10-14 [Judah prospered like a luxuriant vine but God plucked the vine in judgment]]; Mt 3:10 [Divine judgment > fruitless persons would be destroyed like fruitless trees]; Matthew 7:16 see note).

John Piper writes concerning these verses that...

The two fields represent two kinds of persons: one a fruitful person. The other a fruitless person. Three words point to the final condemnation and lostness of the fruitless person. The fruitless field is worthless (Cf. Ro 1:28-note; 2Cor 13:5-7; 1Cor 9:24-25, 26-27; 2 Timothy 3:8-note; Titus 1:16-note - these verses all use adokimos - see notes Hebrews 6:8 ), and it is about to be cursed, and it's end (not means but end) is burning. Worthless, cursed, destined for burning. That is the language of final condemnation...The whole context tells us that more than a simple change of mind is involved (in their "falling away" in Hebrews 6:6). What's involved is a life that is persistently fruitless. That's the point of verse 7 -- the fruitless field. What brings the curse of God down on a person in this text is that they have drunk the rain of God's goodness year after year but have not brought forth any fruit.

The issue of apostasy is not primarily doctrinal, but practical. It's the problem of Hebrews 5:14  (note) where they are unwilling to put there faith into practice, and so their faculties are getting dull, right and wrong are becoming hazy, and the writer says, if you don't stop drifting (Hebrews 2:1-note) and neglecting your salvation (Hebrews 2:3 note) and forsaking the assembling of yourselves together (Hebrews 10:25-note) you are going to be hardened by the deceitfulness of sin and fall away from the living God (Hebrews 3:12-note; Heb 3:13-note).

What exposes a person to the danger of eternal loss in this text is the persistent failure to exercise the organ of faith in pumping the blood of obedience (see notes Hebrews 3:18; 4:11; 5:7; 5:8, 5:9; 10:36; 12:14). The issue at every point in Hebrews 5:11 to Hebrews 6:12 is the neglect of practical holiness not the abandonment doctrinal orthodoxy (as important as that is). And the falling away referred to in Hebrews 6:6 is the point at which the heart becomes so hardened and indifferent that it is beyond help any more.

If you allow yourself to drift down the river of sin with no zealous pursuit of holiness and growth in grace, there will come a point of no return." This is the great folly of those who profess to be Christians but live a carnal life thinking that they will clean things up in their old age.

I've told the story once before of the vulture who spotted the corpse of a fox on a big hunk of ice floating down the river toward Niagara Falls. He flies to the ice, lands and begins to eat the fox. He watches the falls approaching and hears the warnings of danger, but he tells himself that he has wings and is free and does not need to pay attention to such warnings. He is destined for the sky. At the last minute he finishes his feast and spreads his wings but he can't fly because his talons have frozen in the ice and he is dragged over the falls to his destruction.

And so it will be with people who have heard the warnings of scripture to abandon their worldly lusts and pursue holiness, but who say, "I have wings, I am a Christian. I can fly anytime I want to." The day will come when they may try and will not be able to repent because they are so hardened and addicted to the world they can't even feel one genuine spiritual affection (referring to Esau's regret without repentance - example of exposure to the Truth and yet their hardness - Hebrews 12:17 note). (See Piper's full pithy discussion The Doctrine of Perseverance)

F B Hole (Biographical Note) writes that...

The contrast in verses 7 and 8 is not, you notice, between ground which this season is fruitful and the same ground which another season is unfruitful, but between ground which is essentially good and another piece which is essentially bad. The very form of this illustration supports the explanation just given of verses 4 to 6. Judas enjoyed "the rain that cometh oft," yet he only brought forth thorns and briars and was rejected.  (Hebrews Commentary Notes)

Expositor's Bible Commentary writes that...

The process is illustrated from agriculture. There is land that frequently drinks in rain and as a result brings forth a crop. The rain comes first. The land does not produce the crop of itself. The spiritual parallel should not be overlooked. The word translated "a crop" (botane) is a general term for herbage; it does not mean any specific crop. "Useful to those for whom it is farmed" means that the beneficiaries are people in general and not only those who actually work on the farm. This land, then, receives God's blessing. (Gaebelein, F, Editor: Expositor's Bible Commentary 6-Volume New Testament. Zondervan Publishing)

AND BRINGS FORTH VEGETATION USEFUL TO THOSE FOR WHOSE SAKE IT IS ALSO TILLED, RECEIVES A BLESSING FROM GOD:  pollakis hueton kai tiktousa (PAPFSN) botanen eutheton ekeinois di ous kai georgeitai (3SPPI) , metalambanei (3SPAI) eulogias apo tou theou: (Ge 27:27 Lev 25:21 Ps 24:5 Ps 65:10 Ps 126:6 Isaiah 44:3 Ezek 34:26 Hosea 10:12 Mal 3:10)

The rain comes first. The land does not produce the crop of itself. The spiritual parallel is that fruit-bearing is the evidence of a genuine faith and regeneration. Fruit-bearing (cf. John 15:5-6) is the evidence of a true relationship with Christ. The fruit of course is the evidence of and not the means of salvation.

It should be noted that some evangelical commentators like Dr Charles Ryrie feel that the writer is describing loss of rewards in Hebrews 6:6-7.

Brings forth (5088) (tikto) means to be born (of children in Mt 1:21 speaking of Mary declaring "she will bear a Son..."), here of course describing the earth producing or yielding vegetation. The present tense describes ground that continually (as a "lifestyle") gives "birth" to useful vegetation.

Receives  (3335) (metalambano from meta = with, denoting association + lambáno =  receive) means to receive as one's share in or as one's part of. The idea is to share or participate in something.

Blessing (2129) (eulogia from eu = good, well + lógos = word) is literally a good word and by metonymy (figure of speech consisting of use of name of one thing for that of another of which it is an attribute or with which it is associated - e.g., "Washington" for the US government), blessing, favor conferred, gift, benefit, bounty.

Eulogia is the act of speaking in favorable terms (praise) or the benefit of blessing. Here it speaks primarily of the spiritual benefits bestowed by God upon His family members. He blesses because He is ready, willing and able to do so, not because we deserve His blessings or have earned them (it is all of grace). He is the source of all blessing, of every good thing. Goodness can only come from God because there is no source of goodness outside of God (the natural man bristles at truths such as this).

Jon Courson writes that...

Just as rain falls on both briars and fruit-bearing plants, the glorious news of salvation would have been refreshing and renewing to those who understood that salvation is based solely and completely on the finished work of the Cross. But to those who insisted on returning to a works-based relationship with God, the same Word would be damning. (Courson, J: Jon Courson's Application Commentary: NT. Nelson. 2004 or Logos) 

Wycliffe Bible Commentary writes that...

In choosing to reject Christ, the apostates most resembled a field that yields only thorns and thistles, though the rains falling upon it and the farmers tilling were intended to produce beneficial herbs. There can be no mistaking the direct and strong warning to readers tempted to turn away from Christ. Indeed, what was true for these first century believers is still true for believers today. (Pfeiffer, C F: Wycliffe Bible Commentary. 1981. Moody or Logos)

KJV Bible Commentary writes that...

 It should also be noticed that the illustration does not speak of a parcel of land that first produces and later becomes void of life; so it does not illustrate someone saved then lost. (Dobson, E G, Charles Feinberg, E Hindson, Woodrow Kroll, H L. Wilmington: KJV Bible Commentary: Nelson or Logos)

Wuest explains that...

In these verses the writer presents an analogy in nature. The abundant and frequently renewed rain, represents the free and reiterated bestowal of spiritual enlightenment and impulse to these Hebrews. One piece of ground reacts by producing herbage good for food. This is the Hebrew who accepts the New Testament by faith. On the other hand, the ground that receives the same rain, but produces thorns and briers, is likened to the Hebrew who being the recipient of the pre-salvation work of the Spirit, yet turns his back on Him and goes back to the First Testament sacrifices, the apostate who can look for nothing but certain judgment (Hebrews 10:26-31). (Wuest, K. S. Wuest's Word Studies from the Greek New Testament: Eerdmans or Logos)

BUT IF IT YIELDS THORNS AND THISTLES IT IS WORTHLESS: ekpherousa (PAPFSN) de akanthas kai tribolous adokimos : (Heb 12:17 Ge 3:17,18 4:11 5:29 De 29:28 Job 31:40 Ps 107:34 Isaiah 5:1-7 Jer 17:6, 44:22 Mark 11:14,21 Lk 13:7-9 )

Yields (1627) (ekphero from ek = out + phéro = bring, bear, carry) means to bear or carry out, bring forth, or yield. Note the present tense which means if it continually (as a "lifestyle") yields thorns and thistles.

Thorns (173) (akantha from ake = a point or prick) refers to a thorn plant, thistle or brier which abounds with pricks

Thistles (5146) (tribolos from treís = three + bélos = an arrow, dart, or bolís = dart) means three-pointed or three-pronged.

Vincent notes that the tribolos described...

A ball with sharp iron spikes, on three of which it rested, while the fourth projected upward, was called tribulus or tribolos, or caltrop. These were scattered over the ground by Roman soldiers in order to impede the enemy’s cavalry. A kind of thorn or thistle, a land-caltrop, was called tribulus. (Vincent, M. R. Word Studies in the New Testament 4:447)

Worthless (96) (adokimos from a = without + dokimos = tested and thus reliable or acceptable) refers to that which is rejected after a trial or examination because it fails the test. It means to put to the test for the purpose of being approved, but failing to meet the requirements.

Titus 1:16 They profess to know God, but by their deeds they deny Him, being detestable and disobedient, and worthless for any good deed. (see note)

"Many (who) will say to Me on that day, 'Lord, Lord, did we not prophesy in Your name, and in Your name cast out demons, and in Your name perform many miracles?' (see note Matthew 7:22) to whom He declares "I never knew you; DEPART FROM ME, YOU WHO PRACTICE LAWLESSNESS." (see note Matthew 7:23) 

Fruitfulness is a test of genuine nature of a tree or plant and is a metaphor which Jesus Himself frequently used...

Therefore bring forth fruit in keeping with repentance (Mt 3:8)

Even so, every good tree bears good fruit; but the bad tree bears bad fruit. (see note Matthew 7:17)

And the one on whom seed was sown on the rocky places, this is the man who hears the word, and immediately receives it with joy; 21 yet he has no firm root in himself, but is only temporary, and when affliction or persecution arises because of the word, immediately he falls away. (Mt 13:20,21)

And those on the rocky soil are those who, when they hear, receive the word with joy; and these have no firm root; they believe for a while, and in time of temptation fall away. 14 "And the seed which fell among the thorns, these are the ones who have heard, and as they go on their way they are choked with worries and riches and pleasures of this life, and bring no fruit to maturity. (Luke 8:13-14)

And in a similar way these are the ones on whom seed was sown on the rocky places, who, when they hear the word, immediately receive it with joy; and they have no firm root in themselves, but are only temporary; then, when affliction or persecution arises because of the word, immediately they fall away. 18 "And others are the ones on whom seed was sown among the thorns; these are the ones who have heard the word, 19 and the worries of the world, and the deceitfulness of riches, and the desires for other things enter in and choke the word, and it becomes unfruitful. (Mk 4:16-19)

See related notes on assessing the genuineness of one's faith - James 2:14