“hard.” The Hebrew is pala (#06381 פָּלָא), and it means to be marvelous, wonderful, surpassing, extraordinary, to be beyond one’s power. Thus “hard” is an acceptable translation, especially in light of the fact that “wonderful” in Hebrew had the connotation of hard or beyond one’s ability, but it does not carry that overtone in English. Nevertheless, “hard” and “wonderful” are both conveyed in the Hebrew in this verse: Sarah’s getting pregnant is not too hard for Yahweh, and it is indeed “wonderful.”

“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).