Paul ties words together, and the bundle of words he creates exclude others. The words in his bundle are promise, faith, grace, and “all” and these words are tied together by “God” and “family.” God’s promise to Abraham, to make him a father of many nations (Gen. 17:5) — the big family, is by faith and therefore by grace. Therefore, it is not by Law and it not limited simply to those who are of the Law (Jews) — little family. So, Romans 4:16-17.
As Tom Wright puts it, “the universal availability of the promise is Paul’s main thrust.” Wright says the main subjects of chp. 4 are Abraham, his family, and his God. His suggestion is worth more consideration: there is some clipped syntax in 4:16-17, and it fills in gaps left open in 4:1-2. It is about what is going on “before God.”
This God, as Paul finishes off 4:17, gives life to the dead. He brings this out of nothing — and this surely describes the arise of faith in the Gentile. The Gentile comes to faith in spite of not having the Torah.