Cheryl Schatz

The reason that the sin nature had to be passed on to all (except for the seed of the woman) is because we were all to be shut up under sin so that salvation would come through faith and not by works.

Galatians 3:22 (NASB)
22 But the Scripture has shut up everyone under sin, so that the promise by faith in Jesus Christ might be given to those who believe.

Romans 11:32 (NASB9)
32 For God has shut up all in disobedience so that He may show mercy to all.

The term “shut up” means:

to catch by enclosing, close up together, hem in, enclose…confine imprison
Arndt, W., Danker, F. W., & Bauer, W. (2000). A Greek-English lexicon of the New Testament and other early Christian literature (3rd ed.)

It is the sin nature that “catches” us and imprisons us and makes every single one of us needy so that none of us can claim to be sinless and having “earned” salvation.

If some were able to be sinless of their own ability, then salvation would not be needed by all. God has in His providential will allowed all to be “shut up” in disobedience through the sin nature that came through Adam. When we are caught in that sin trap, we are able to understand that we need a Savior. And none of us is in a better boat because all have sinned and come short of the glory of God. The fact that the sin nature comes upon all of us leaves us without hope in the world, but able to seek for and find the Savior by His own drawing us to Himself.