“return, yes, return.” This is the figure of speech polyptoton, where the verb “return” is repeated twice but in different cases, emphasizing that God will return. Another English translation might be “absolutely return,” or “surely return,” but those miss the poetic beauty of “return, return.” God is assuring Abraham that Sarah will indeed have a son. [For more on the figure polyptoton and the emphasis it brings, as well as the way it is translated in the REV, see commentary on Genesis 2:16].

“according to the time of life.” The Hebrew text is, “according to the time of life” but that is considered an idiom, although it may be literal and refer to the time of pregnancy (see commentary on 2 Kings 4:16).