17:17י״ז:י״ז
1 א

ויפל אברהם על פניו ויצחק. זֶה תִּ"אֻ, לְשׁוֹן שִׂמְחָה, וַחֲדִי, וְשֶׁל שָׂרָה לְשׁוֹן מָחוֹךְ; לָמַדְתָּ שֶׁאַבְרָהָם הֶאֱמִין וְשָׂמַח וְשָׂרָה לֹא הֶאֱמִינָה וְלִגְלְגָה, וְזֶהוּ שֶׁהִקְפִּיד הַקָּבָּ"ה עַל שָׂרָה וְלֹא הִקְפִּיד עַל אַבְרָהָם:

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.

2 ב

הלבן. יֵשׁ תְּמִיהוֹת שֶׁהֵן קַיָּמוֹת, כְּמוֹ הֲנִגְלֹה נִגְלֵיתִי? (שמואל א ב'), הֲרֹאֶה אַתָּה (יח' ח'), אַף זוֹ הִיא קַיֶּמֶת; וְכָךְ אָמַר בְּלִבּוֹ, הֲנַעֲשָׂה חֶסֶד זֶה לְאַחֵר, מַה שֶּׁהַקָּבָּ"ה עוֹשֶׂה לִי?

הלבן SHALL A CHILD BE BORN TO ONE WHO IS A HUNDRED YEARS OLD? — There are some questions expressing astonishment which do not imply a doubt but rather affirm the certainty that the circumstance referred to has happened or will happen, as (1 Samuel 2:2) “Did I reveal myself [unto thy father’s house?]” (Of course, I did) and (Ezekiel 8:6) “Seest thou what they do?” (You, of course, have seen it). This question, too, affirms the certainty that it is possible for God to cause Abraham, at the age of hundred, to beget a son and this is in effect what he said to himself: Would there be done to another man one hundred years old this favour that the Holy One, blessed be He, is doing to me”? (Rashi means that the words must be translated, “would a child be born to any other person who is a hundred years old?”).

3 ג

ואם שרה הבת תשעים שנה. הָיְתָה כְדַאי לֵילֵד; וְאַף עַל פִּי שֶׁדּוֹרוֹת הָרִאשׁוֹנִים הָיוּ מוֹלִידִין בְּנֵי ת"ק שָׁנָה, בִּימֵי אַבְרָהָם נִתְמָעֲטוּ הַשָּׁנִים כְּבָר וּבָא תַּשּׁוּת כֹּחַ לָעוֹלָם, צֵא וּלְמַד מֵעֲשָׂרָה דּוֹרוֹת שֶׁמִּנֹּחַ וְעַד אַבְרָהָם, שֶׁמִּהֲרוּ תּוֹלְדוֹתֵיהֶן בְּנֵי ס' וּבְנֵי ע':

ואם שרה הבת תשעים שנה OR SHALL SARAH, WHO IS NINETY YEARS OLD be worthy to bear a son? Although the previous generations used to beget at the age of five hundred years, yet in Abraham’s days the length of life had already become shorter and a diminution of strength had come upon people. Go and learn this from the ten generations from Noah to Abraham who begot their children at the then early age of sixty or seventy.