Genesis 17:17
15 Then God said to Abraham, “As for your wife, you must no longer call her Sarai; Sarah will be her name. 16 I will bless her and will give you a son through her. I will bless her and she will become a mother of nations. Kings of countries will come from her!” 17 Then Abraham bowed down with his face to the ground and laughed as he said to himself, “Can a son be born to a man who is a hundred years old? Can Sarah bear a child at the age of ninety?” 18 Abraham said to God, “O that Ishmael might live before you!” 19 God said, “No, Sarah your wife is going to bear you a son, and you will name him Isaac. I will confirm my covenant with him as a perpetual covenant for his descendants after him.
Onkelos Genesis 17:17
15 And the Lord said to Abraham, The name of Sara thy wife shall not be called Sara, for Sarah shall be her name: 16 and I will bless her, and I will also give thee a son from her; and I will bless her, and assemblies and kings which have dominion over peoples from her shall be. 17 And Abraham fell upon his face and rejoiced, and said in his heart, Will the son of a hundred years have a child, and Sarah the daughter of ninety years bring forth? 18 And Abraham said before the Lord, O that Yishmael may be established before thee! 19 And the Lord said, In verity Sarah thy wife shall bear thee a son, and thou shalt call his name Izhak; and I will establish My covenant with him for an everlasting covenant to his sons after him.
Notes and References
"... The ancient and medieval commentators did not understand Abraham’s laughter in this manner. Already the Book of Jubilees, whose fifteenth chapter is an almost verbatim paraphrase of Genesis 17, states, “And Abraham fell on his face and rejoiced” (Jubilees 15:17), an interpretation shared by the Septuagint. The ancient Aramaic Targumim follow a similar path. Thus, for example, Onkelos: (And Abraham fell on his face and rejoiced), followed by Rashi. Similarly, Rav Sa’adya Gaon (va-yismaḥ), Kimhi (samaḥ be-libo), and Nahmanides. The identification of Abraham’s laughter as an expression of joy dictates in turn their explanations further along in the chapter. Thus, regarding Abraham’s question, “Shall a child be born to a man who is a hundred years old?,” Rashi writes: “There are expressions of astonishment that are fulfilled [i.e., rhetorically] ... So was this one [as if it had been] fulfilled. Thus he said in his heart, ‘Shall this kindness be done after all that the Holy One, blessed be he, has done for me?’ ” Abraham, according to Rashi, is self-effacing: “‘Would that Ishmael would live before you’ - I am not worthy to receive such a reward ..."
Lorberbaum, Yair Yitshak and God’s Separation Anxiety (pp. 105-142) Journal of Jewish Thought & Philosophy, No., 2013