Romans 9:9-12

Why would Paul want to make sure that we understood this?

These verses make sure that anybody who heard Paul or read the words that he wrote, which is now Scripture, would understand clearly that absolutely no works of his had anything at all to do with God's choice of him to be an apostle to the Gentiles. No works of Jacob made God choose Jacob. Jacob was set apart in the womb, and Paul is claiming the same thing. No works of Paul made God call him, because he too was set apart in the womb before he did anything.

It is important for us to understand this, that what matters is what God did, and what we do after God does what He does; that is, following conversion. But there is something else that I think is worth considering too. If God did set Paul apart from the womb, then it is highly likely that God guided and directed him through his entire education—the education that Paul received long before God ever called him directly into His service as an apostle. Paul was admirably and thoroughly trained in the basic foundation of Old Covenant law without his ever knowing, until his calling, what its real use would be.