4:16 That is why it depends on faith. Because the promise in all its elements is received by faith, it also rests “on grace.” Had it been on the basis of works, the promise would have failed; had it been on the basis of circumcision, it could have been received only by Jews. Because it is by faith, and therefore by grace (by God’s action, not man’s), it is “guaranteed” to come to Abraham’s true spiritual offspring, or all believers whether Jew or Gentile by birth.