I know it’s in Genesis. My question is, was that part of Genesis already written when Abraham was alive?
The Syriac Peshitta reads:
“Because God knew in advance that the Gentiles would be declared righteous through faith, He first preached to Abraham, as it is said in the Holy Scriptures, “In you shall all the gentiles be blessed.”
I’m inclined to agree with Gill on this passage that the Syriac has it right.