A proper understanding of the law of God is the single most difficult thing for Christians to grasp. Mat 5:17 is one of the most misunderstood scriptures in all of the Bible.

Mat 5:17 Think not that I am come to destroy the law, or the prophets: I am not come to destroy, but to fulfil.

Everyone seems to understand that Christ fulfilled the prophecies of Himself but no one seems to be able to get a handle on the fact that He is also our sabbath, and through the death in His flesh he has also fulfilled the ‘law which is made for an unrighteous man.’

1Ti 1:9 Knowing this, that the law is not made for a righteous man, but for the lawless and disobedient, for the ungodly and for sinners, for unholy and profane, for murderers of fathers and murderers of mothers, for manslayers,

Christ, of course, was a ‘righteous man.’ And yet He came in flesh which ‘cannot inherit the kingdom of God.’

1Co 15:50 Now this I say, brethren, that flesh and blood cannot inherit the kingdom of God; neither doth corruption inherit incorruption.

Adam was from the creators hand made flesh. Now what is it that we are told of flesh?:

1Co 15:50 Now this I say, brethren, that flesh and blood cannot inherit the kingdom of God; neither doth corruption inherit incorruption.

According to this and all of scripture flesh and blood are corruptible. That is why Eve lusted after the fruit on that tree before she ever touched the tree. Eating of the fruit was not the first sin committed by Eve. Eating of that fruit was the result of the sin that Eve committed because she was mere corruptible flesh and blood. Eve committed the sin of covetousness and lust before she ever touched the tree of the knowledge of good and evil. Eve had no real hope of doing otherwise under the circumstances. She, as we all are was operating under an unrelenting “law.”

Rom 8:2 For the law of the Spirit of life in Christ Jesus hath made me free from the law of sin and death.

That is why David could say of his mother, of whom we have no record of immorality:

Psa 51:5 Behold, I was shapen in iniquity; and in sin did my mother conceive me.

Adam could say this same thing of his shaping and conception. What we fail to understand is that flesh, being corruptible, in scriptural terms IS sin. That is what is meant by:

Gal 4:4 But when the fulness of the time was come, God sent forth his Son, made of a woman, made under the law,

Being “made of a woman,” is what made Christ to be “made to be sin for us.”

2Co 5:21 For he hath made him [ to be] sin for us, who knew no sin; that we might be made the righteousness of God in him.

The words “to be” are not in the original Greek. Christ was simply “made sin” by virtue of being “born of a woman.” That part was accomplished at His conception, long before He was put on the cross.
So what does Heb 5:7 mean when it is translated as “through death?” It would say “to him [ God] who was able to save him [ Jesus] through death…” Why would Jesus need to be saved through death?” Christ’s “flesh and blood can no more inherit the kingdom of God than can our flesh and blood.” That is one reason why we are told:

2Co 5:16 Wherefore henceforth know we no man after the flesh: yea, though we have known Christ after the flesh, yet now henceforth know we him no more [ after the flesh].
2Co 5:17 Therefore if any man be in Christ, he is a new creature: old things are passed away; behold, all things are become new.

The flesh was created, like the ugly scaffolding of a beautiful building, to be taken down and never seen again.