Comentario sobre Génesis 17:17

ויפל אברהם על פניו ויצחק AND ABRAHAM FELL UPON HIS FACE AND LAUGHED — This word ויצחק Onkelos translates by וחדי which signifies joy (“and he rejoiced’’) but the similar verb in the case of Sarah (ותצחק Genesis 18:12) he translates as meaning laughter. From this you may understand that Abraham had faith and rejoiced, and that Sarah had no faith and sneered, and that is why God was angry with Sarah (when she laughed) but was not angry with Abraham.

‘VAYITZCHAK’ (AND HE LAUGHED). Onkelos translated: “and he rejoiced.” This is correct since the word tzachak can be used intermittently for sporting or rejoicing, just as in the verses: ‘Mesacheketh’ (Sporting) in His habitable earth,⁴³²Proverbs 8:31. ‘mesachkim’ (rejoiced) before the Eternal.⁴³³II Samuel 6:5.
In my opinion the intent of this expression is to convey the thought that whoever sees a favorable unusual event in one’s life rejoices to the point where “his mouth is filled with laughter.”⁴³⁴Psalms 126:2. It is this thought which Sarah expressed: G-d hath made laughter for me; everyone that heareth will laugh on account of me,⁴³⁵Further, 21:6. just as in the verse, Then was our mouth filled with laughter, and our tongue with singing.⁴³⁴Psalms 126:2. And this is what Abraham did. When this good tiding was related to him, he rejoiced and his mouth was filled with laughter, and he said in his heart that this is an occasion for rejoicing as it is a very wonderful matter. Shall a child be born unto him that is a hundred years old? and shall Sarah, that is ninety years old, bear? And will this matter not give cause for rejoicing and happiness? Only, Scripture speaks summarily of his wonderment, as it is connected with the word vayitzchak. A similar case is the expression, Have I even here seen,⁴³⁶Above, 16:13. which is connected with the beginning of the verse: for she [Hagar] said, “Have I even here seen G-d, revealing to me that He saw in my affliction, and shall I not call Him E-il-ro’i [the G-d who seeth me]?” Another such example is the expression, Did I reveal Myself unto the house of thy father,⁴³⁷I Samuel 2:27. which is connected with the following verse, Why do you kick at My sacrifice and at Mine offering,⁴³⁸Ibid., Verse 29. thus stating, “Have I chosen you so that you kick at My sacrifice and Mine offering? Why then do you do so?”
It may be that the question, Shall a child be born to him that is a hundred years old? is an expression of amazement, not one of impossibility, just as in the verse, Wilt thou judge the bloody city,⁴³⁹Ezekiel 22:2. which means, “Do you want to judge her and cause her to know all her abominations?” A similar case is the verse, Wilt thou set thine eyes upon it? it is gone.⁴⁴⁰Proverbs 23:5. Likewise is the verse, Hast thou eaten of the tree, whereof I commanded thee that thou shouldst not eat?⁴⁴¹Above, 3:11. That is to say, “Has the thought occurred to you to eat of the tree?” This verse likewise is saying, “Has the thought occurred to anyone that a child be born to him that is a hundred years old, and that Sarah, who is ninety years, shall bear?” After that Abraham said to Him that he wishes this miracle be with the life of Ishmael.⁴⁴²Verse 18 here.

?הלבן מאה שנה יולד; He meant that although it is possible for a woman to become pregnant after her prime, when this occurs it is only when she sleeps with a younger man. It has not been known to occur when her partner is also an old man.