Here "the promise may rest on grace" represents God giving what he promised because of his grace. AT: "so that what he promised might be a free gift" or "so that his promise would be because of his grace" (See: [[rc://en/ta/man/translate/figs-metaphor]])
This can be stated in active form. AT: "all of Abraham's descendants might certainly receive what God has promised to give" (See: [[rc://en/ta/man/translate/figs-activepassive]])
Here the word "us" refers to Paul and includes all Jewish and non-Jewish believers in Christ. Abraham is the physical ancestor of the Jewish people, but he is also the spiritual father of those who have faith. (See: [[rc://en/ta/man/translate/figs-inclusive]])
Where it is written can be made explicit. You can also translate this in an active form. AT: "as someone has written in the Scriptures" (See: [[rc://en/ta/man/translate/figs-explicit]] and [[rc://en/ta/man/translate/figs-activepassive]])
Here "of him whom he trusted" refers to God. AT: "Abraham was in the presence of God whom he trusted, who gives life to those who have died" (See: [[rc://en/ta/man/translate/figs-explicit]])