THEREFORE SINCE THE CHILDREN SHARE IN FLESH AND BLOOD: epei oun ta paidia kekoinoneken (3SRAI) haimatos kai sarkos:

Children (3813) (paidion from diminutive of país = child) refers literally to a child or children recently born. Here it is a figurative endearing appellation for the followers of Christ,  human beings who are the subjects of the redemption that is in Christ Jesus.

Share (2841) (koinoneo from koinos = common, shared by all) means to have a share in common with someone else. The idea is to share one's possessions with the implication of some kind of joint participation and mutual interest. The human race has in common flesh and blood.

Spurgeon writes...

As you know to your cost, for perhaps you have aches and pains about you at this very moment. Verily, you are “partakers of flesh and blood.” Perhaps you are suffering from despondency and depression of spirit. If so, that reminds you that, however much you may, in spirit, sometimes soar to heaven, yet you are still “partakers of flesh and blood.”

Flesh and blood -- The order in the Greek text is “blood and flesh.” In the rabbinical writers, this was a technical phrase speaking of human nature in contrast with God. Jesus  set aside the outward display of His deity and veiled His Godhead in a “robe of clay.” But He did not stop at Bethlehem. “All the way to Calvary He went for me because He loved me so.”

Flesh (4561) (sarx) refers to the covering  of a living creature. Note that "flesh" is one of those words that one must be careful to interpret because it has a wide range of meanings depending on the context (See word study)

Blood (blood) (haima) is the fluid with its constituents (red blood cells, etc) that forms the basis for life by transporting oxygen from the lungs to all the body parts. Without blood there is no life.

Regarding the spiritual significance of the blood Moses records that...

the life of the flesh is in the blood, and I have given it to you on the altar to make atonement for your souls; for it is the blood by reason of the life that makes atonement...as for the life of all flesh, its blood is identified with its life. Therefore I said to the sons of Israel, 'You are not to eat the blood of any flesh, for the life of all flesh is its blood; whoever eats it shall be cut off.' (Leviticus 17:11, 14)

The angels fell, and remained without hope or help. Christ never designed to be the Saviour of the fallen angels. Therefore He did not take their nature; and the nature of angels could not be an atoning sacrifice for the sin of man. Here is a price paid, enough for all, and suitable to all, for it was in our nature. Here the wonderful love of God appeared, that, when Christ knew what he must suffer in our nature, and how he must die in it, yet he readily took it upon Himself.

This atonement made way for God's people's to be delivered from Satan's bondage, and to provide the ransom payment for the pardon of their sins which became effective through personal belief in these truths. In light of the truth in this passage, believers who dread death, and strive to get the better of their terrors, need no longer attempt to outbrave or to stifle them.

HE HIMSELF LIKEWISE ALSO PARTOOK OF THE SAME: kai autos paraplesios meteschen (3SAAI) ton auton:

Spurgeon writes...

Christ’s great mission was not to save angels, but to save men. Therefore he came not in the nature of angels, but in the nature of men.

He so took upon his flesh and blood as to die in our nature, that thus he might slay death, and might set us free from all fear of death. Do you not see that, if the representative Man, Christ Jesus, died, he also rose again, and that so also will all who are in him rise, too? If you are in him, you shall rise again. Therefore, fear not to lie down in your last sleep, for the trumpet shall awaken you, and your bodies shall be molded afresh like unto his glorious body, and your soul and body together shall dwell in infinite bliss for ever.

“Wherefore comfort one another with these words.”

We know what it is to be partakers of flesh and blood; we often wish that we did not. It is the flesh that drags us down; it is the flesh that brings us a thousand sorrows. I have a converted soul, but an unconverted body. Christ has healed my soul, but He has left my body still to a large extent in bondage, and therefore it has still to suffer; but the Lord will redeem even that. The redemption of the body is the adoption, and that is to come at the day of the resurrection. But think of Christ, Who was a partaker of the Eternal Godhead, condescending to make Himself a partaker of flesh and blood; — the Godhead linked with materialism; the Infinite, an infant; the Eternal prepared to die, and actually dying! Oh, wondrous mystery, this union of Deity with humanity in the person of Christ Jesus our Lord!

Likewise (3898) (paraplesios from para = close to or alongside + plesios --nearby, near - Greek word for neighbor derived from plesios!) means in a manner near by, similarly, likewise, coming near, nearly, resembling, in like manner. Expressing general similarity. The Lord Jesus, in His incarnation, took His place alongside and nearby the human race in a somewhat similar manner. It was not altogether in a like manner because Jesus, unlike men, was conceived and born not in sin (Heb 4:15). Jesus was not a mere semblance of a body, as the heresy of Docetism taught (they say He was a "phantom" and it just looked like He had a body but it wasn't a real body - this is overt heresy for it could never secure redemption through His blood).

Partook (3348) (metecho from metá = with, denoting association + écho = have) means literally to hold with and so share in the possession of something or have a share of. It has to do with taking hold of something that is not naturally one's own kind. Christ was not in His natural existence flesh and blood. And yet He willingly "took hold" of something which did not naturally belong to Him. One of the requirements of a kinsman-redeemer (see discussion of Goel = Kinsman Redeemer) in the Old Testament was to be related to the one for which the redemption was undertaken. Jesus our Goel, our nearest Kinsman-Redeemer took on Himself our nature in order that He might die in our place, paying the price of redemption, which in turn would liberate us take hold of the divine nature that did not belong to us. Peter writes about this in his second letter...

For by these (His own glory and excellence) He has granted to us His precious and magnificent promises, in order that by them you might become partakers of the divine nature, having escaped the corruption that is in the world by lust. (See note 2 Peter 1:4)

Adam sinned and forfeited his right of dominion over this earth. The forfeited inheritance (according to Jewish law) was ransomed by the nearest of kin and so Jesus became our nearest of kin by taking on humanity, in order to become our Goel or Kinsman-Redeemer.

Partook or "had a part in" is  the aorist tense (past completed action) which points to the historical event of His incarnation, when He became Man and accordingly one with mankind!

It is notable that the writer did not use the same word he used for men sharing life with men, the word koinonia which marks the characteristic sharing of the common fleshly nature (including the sin of Adam) as it pertains to the human race at large. On the other hand metecho (took part of) speaks of the unique fact of the incarnation as a voluntary acceptance of humanity. Thus, our Lord took hold of human nature without its sin in the incarnation, and held it to Himself as an additional nature (the perfect God-Man, fully God, fully Man, a truth not fully comprehensible to finite man), thus associating Himself with the human race in its possession of flesh and blood. He took to Himself, something with which by nature He had nothing in common (metecho), flesh and blood. Human beings possess human nature in common with one another (koinonia). The Son of God united with Himself, something that was not natural to Him.

Vincent writes that koinonia marks...

the characteristic sharing of the common fleshly nature as it pertains to the human race at large, and the former (metecho) signifying the unique fact of the incarnation as a voluntary acceptance of humanity.

What light this throws upon the Bible’s attitude towards the dual nature of our Lord, Very God and Very Man! And He did this all for us!

His birth didn’t save anyone but by His death He saves us. It was not His birth or His life but His death which brought to us salvation and deliverance from spiritual and eternal death. He could not have undergone death as God but only by becoming man. Not by Almighty power but by His death He overcame death.

THAT THROUGH DEATH HE MIGHT RENDER POWERLESS HIM WHO HAD THE POWER OF DEATH THAT IS THE DEVIL: hina dia tou thanatou katargese (3SAAS) ton to kratos echonta (PAPMSA) tou thanatou tout estin (3SPAI) ton diabolon:

That (hina = introduces a purpose clause) - Here the purpose of Jesus' incarnation is clearly given - to render powerless, idle, inoperative or ineffective the devil's power of death.

Through (1223) (dia) is a preposition denoting instrumentality, the means by which something is accomplished, in this case the de-fanging of the devil's power over those who have been delivered from the kingdom of darkness and transferred to the kingdom of light, of God's Beloved Son.

Death (2288) (thanatos) is literally a physical separation of the soul from the body. Every form of death in the NT is treated not as a natural process but always as a destroying power related to sin and its consequences. This is certainly true in the case of the sinless God Man...

He (God the Father) made Him (Jesus the Son) Who knew no sin to be sin on our behalf, that we might become the righteousness of God in Him. (2 Cor 5:21)

Spurgeon writes...

That, through dying, he might overthrow Satan’s power for all who trust him.

By his own death, Christ broke that evil power which brought death into the world with its long trail of woe. He did this, not by his example, not even by his life, but by his death. Therefore let those who speak slightingly of his atoning sacrifice see their folly, for it is through death that Christ destroys “him that had the power of death, that is, the devil“

Render powerless (2673) (katargeo from kata = intensifies meaning + argeo = be idle from argos = ineffective, idle, inactive from  a = without + érgon = work) (Click word study on katargeo) literally means to reduce to inactivity. The idea is to make the power or force of something ineffective and so to render powerless, reduce to inactivity. To do away with. To put out of use.  To cause to be idle or useless. To render entirely idle, inoperative or ineffective. Cause something to come to an end or cause it to cease to happen. To abolish or cause not to function. To free or release from an earlier obligation or relationship. To no longer take place. Katargeo always denotes a nonphysical destruction by means of a superior force coming in to replace the force previously in effect, as e.g. light destroys darkness.

Katargeo in his verse means the loss of well-being rather than loss of being. It means to nullify or to bring to nothing. Satan is still actively opposing the purposes of God in the world, but he received a death wound at the cross. His time is short and his doom is sure. He is a defeated foe.

Barnes writes that...

"The word “destroy” here is not used in the sense of “closing life,” or of “killing,” but in the sense of bringing into subjection, or crushing his power. This is the work which the Lord Jesus came to perform - to destroy the kingdom of Satan in the world, and to set up another kingdom in its place."

Power (2904) (kratos) (Click word study on kratos) means strength or might, especially manifested power, the power to rule or control or dominion (power to rule, supreme authority, sovereignty, the right to govern or rule or determine). Krátos denotes the presence and significance of force or strength rather than its exercise. It is the ability to exhibit or express resident strength.

MacDonald explains the devil's "power of death" as follows...

In what sense does the devil have the power of death? Probably the chief sense in which he has this power is in demanding death. It was through Satan that sin first entered the world. God’s holiness decreed the death of all who sinned. So in his role as adversary, the devil can demand that the penalty be paid.  In heathen lands his power is also seen in the ability of his agents, the witch doctors, to pronounce a curse on a person and for that person to die without any natural cause.  There is no suggestion in Scripture that the devil can inflict death on a believer without the permission of God (Job 2:6), and therefore he cannot set the time of a believer’s death. Through wicked men, he is sometimes permitted to kill the believer. But Jesus warned His disciples not to fear those who could destroy the body, but rather to fear God who can destroy both soul and body in hell (Matt. 10:28).  In the OT, Enoch and Elijah went to heaven without dying. No doubt this was because, as believers, they were reckoned to have died in the still-future death of Christ.  When Christ comes at the Rapture, all living believers will go to heaven without dying. But they too escape death because God’s holiness was satisfied for them in the death of Christ. The risen Christ now has “the keys of Hades and of Death” (Rev. 1:18), that is, He has complete authority over them. (MacDonald, W & Farstad, A. Believer's Bible Commentary: Thomas Nelson)

Kenneth Wuest explains that...

Satan was not annihilated at the Cross. His power was broken. Spiritual death cannot hold the person who puts his faith in the Saviour. Physical death cannot keep his body in the grave. The resurrection of the Lord Jesus provides the believer with eternal life, and his body with glorification at the Rapture. Thus, Jesus conquered death, and brought to naught the Devil. Satan had the power of death, not in the sense that he had power over death, but that he had the sovereignty or dominion of death. He had a sovereignty of which death is the realm. The word for “power” in the Greek text here is kratos, which means “power in the sense of dominion.” His dominion over the human race was in the form of death. That dominion is now broken. (Wuest, K. S. Wuest's Word Studies from the Greek New Testament: Eerdmans)

Devil (1228) (diabolos from diá = through, between + ballo = to cast, throw) (Click word study on diabolos) means a false accuser, slanderer (one who utters false charges or misrepresentations which defame and damage another’s reputation), backbiting (malicious comment about one not present), one given to malicious gossip or a calumniator (one who utters maliciously false statements, charges, or imputations about, this term imputes malice to the speaker and falsity to the assertions).

Diabolos is applied some 34 times to Satan, the god of this world, and in each case has the definite article in the Greek ("the" = defining a specific entity) and is never in the plural (the three uses below in the pastoral epistles are all plural) as when applied to men. (See discussion of the prince of the power of the air under whose authority we all "walked" or lived when we were still spiritually dead in our transgressions and sins - Ephesians 2:2)

By virtue of faith in Christ's death and His blood, and His burial and His resurrection the devil's grip on men was broken.

(Jesus told Paul that He delivered him) from the Jewish people and from the Gentiles, to whom I am sending you,  to open their eyes so that they may turn from darkness to light and from the dominion of Satan to God, in order that they may receive forgiveness of sins and an inheritance among those who have been sanctified by faith in Me.' (Acts 26:17-18)

In a parallel passage we read that Jesus...

delivered us from the domain of darkness, and transferred us to the kingdom of His beloved Son, in Whom we have redemption, the forgiveness of sins. (See note Colossians 1:13; Colossians 1:14)

Spiritual death cannot hold the person who puts his faith in the Saviour. Physical death cannot keep his body in the grave. The resurrection of the Lord Jesus provides the believer with eternal life the moment of salvation, and provides him with his glorified imperishable, immortal body at the Rapture. Thus, Jesus conquered death, and brought to naught the Devil.

Though Satan would seek to impose physical death on the whole human race if he could, he can only bring about a particular death when God allows it for some greater purpose (Job 2:4-6; 1 Co 5:5). Satan had the power of death not in the sense that he had power over death but that he had the sovereignty (kratos) of this present world which death is the realm. Kratos means “power in the sense of dominion.” His dominion over the human race is now broken for those who receive Messiah's sacrifice as atonement for their sins.

Paul in discussing the believer's future glorified body says that...

when this perishable will have put on the imperishable, and this mortal will have put on immortality, then will come about the saying that is written, "DEATH IS SWALLOWED UP in victory. "O DEATH, WHERE IS YOUR VICTORY? O DEATH, WHERE IS YOUR STING?" The sting of death is sin, and the power of sin is the law; but thanks be to God, who gives us the victory through our Lord Jesus Christ. (1Corinthians 15:54-57)

Jesus took away the "sting of death" which is "sin" because it is by sin that death gains authority over man, and the power of sin is the law because the law stirs up sin (Ro 5:12; 7:8-11).

Paul explains this relationship to sin and death writing...

Therefore just as through one man sin entered into the world, and death through sin, and so death spread to all men, because all sinned (See notes Romans 5:12)

Writing to Timothy Paul explained that Jesus

now has been revealed by the appearing of our Savior Christ Jesus, who abolished (katargeo = made it ineffective for believers) death, and brought life and immortality to light through the gospel (See note 2 Timothy 1:10) (Comment: Christ abolished death by bearing the sins of men on the cross. As a result, death has now lost its sting for the believer [see above 1 Cor. 15:55]. In the resurrection, Christ conquered death for all believers [1 Cor. 15:20, 48]. For them, to die is gain because to die is to be with Christ [see notes Philippians 1:21, 1:23]. The believer whose body is in the grave will rise bodily when Christ returns for His own [1 Thess. 4:14-17]. As with Christ, so for the believer, there will be no more death [Rev. 20:6; 21:4])

Just to make sure we understand - how did Jesus render powerless the devil who had the power of sin? First, note that implication is that death itself is a power which, though originally foreign to human nature, now reigns over it (See notes Romans 5:12). The devil w