When Avram was ninety-nine, Hashem appeared to him: "Walk before Me and be wholehearted." Then He gave him a new name: "No longer will you be called Avram — your name is Avraham, because I have made you the father of a multitude of nations." And Sarai became Sarah! "Sarah will have a son," Hashem said, "and you will call him Yitzchak." Tzofia tried out her own name with a new letter. Aviya closed the Chumash, smiling. "Next week," she said, "we meet Yitzchak."
From the Torah
1 וַיְהִי אַבְרָם בֶּן־תִּשְׁעִים שָׁנָה וְתֵשַׁע שָׁנִים וַיֵּרָא יְהוָה אֶל־אַבְרָם וַיֹּאמֶר אֵלָיו אֲנִי־אֵל שַׁדַּי הִתְהַלֵּךְ לְפָנַי וֶהְיֵה תָמִים׃
17:1 And when Avram was ninety nine years old, the Lord appeared to Avram, and said to him, I am the Almighty God; walk before Me, and be perfect.
2 וְאֶתְּנָה בְרִיתִי בֵּינִי וּבֵינֶךָ וְאַרְבֶּה אוֹתְךָ בִּמְאֹד מְאֹד׃
17:2 And I will make My covenant between Me and thee, and will multiply thee exceedingly.
3 וַיִּפֹּל אַבְרָם עַל־פָּנָיו וַיְדַבֵּר אִתּוֹ אֱלֹהִים לֵאמֹר׃
17:3 And Avram fell on his face: and God talked with him, saying,
4 אֲנִי הִנֵּה בְרִיתִי אִתָּךְ וְהָיִיתָ לְאַב הֲמוֹן גּוֹיִם׃
17:4 As for Me, behold, My covenant is with thee, and thou shalt be a father of many nations.
5 וְלֹא־יִקָּרֵא עוֹד אֶת־שִׁמְךָ אַבְרָם וְהָיָה שִׁמְךָ אַבְרָהָם כִּי אַב־הֲמוֹן גּוֹיִם נְתַתִּיךָ׃
17:5 Neither shall thy name any more be called Avram, but thy name shall be Avraham; for a father of many nations have I made thee.
15 וַיֹּאמֶר אֱלֹהִים אֶל־אַבְרָהָם שָׂרַי אִשְׁתְּךָ לֹא־תִקְרָא אֶת־שְׁמָהּ שָׂרָי כִּי שָׂרָה שְׁמָהּ׃
17:15 And God said to Avraham, As for Saray thy wife, thou shalt not call her name Saray, but Sara shall her name be.
16 וּבֵרַכְתִּי אֹתָהּ וְגַם נָתַתִּי מִמֶּנָּה לְךָ בֵּן וּבֵרַכְתִּיהָ וְהָיְתָה לְגוֹיִם מַלְכֵי עַמִּים מִמֶּנָּה יִהְיוּ׃
17:16 And I will bless her, and give thee a son also of her: and I will bless her, and she shall be a mother of nations; kings of peoples shall issue from her.
17 וַיִּפֹּל אַבְרָהָם עַל־פָּנָיו וַיִּצְחָק וַיֹּאמֶר בְּלִבּוֹ הַלְּבֶן מֵאָה־שָׁנָה יִוָּלֵד וְאִם־שָׂרָה הֲבַת־תִּשְׁעִים שָׁנָה תֵּלֵד׃
17:17 Then Avraham fell upon his face, and laughed, and said in his heart, Shall a child be born to him that is a hundred years old? and shall Sara, that is ninety years old, give birth?
18 וַיֹּאמֶר אַבְרָהָם אֶל־הָאֱלֹהִים לוּ יִשְׁמָעֵאל יִחְיֶה לְפָנֶיךָ׃
17:18 And Avraham said to God, O that Yishma᾽el might live before thee!
19 וַיֹּאמֶר אֱלֹהִים אֲבָל שָׂרָה אִשְׁתְּךָ יֹלֶדֶת לְךָ בֵּן וְקָרָאתָ אֶת־שְׁמוֹ יִצְחָק וַהֲקִמֹתִי אֶת־בְּרִיתִי אִתּוֹ לִבְרִית עוֹלָם לְזַרְעוֹ אַחֲרָיו׃
17:19 And God said, Sara thy wife shall bear thee a son indeed; and thou shalt call his name Yiżĥaq: and I will establish My covenant with him for an everlasting covenant, and with his seed after him.