וַיֹּ֤אמֶר אֱלֹהִים֙ אֶל־אַבְרָהָ֔ם שָׂרַ֣י אִשְׁתְּךָ֔ לֹא־תִקְרָ֥א אֶת־שְׁמָ֖הּ שָׂרָ֑י כִּ֥י שָׂרָ֖ה שְׁמָֽהּ׃
И сказал Бог Аврааму: 'Что касается Сары, жены твоей, не называй ее имя Сара, но Сарра будет ее именем.
The Midrash of Philo
Why does God say, "Sara thy wife shall not be called Sara, but Sarra shall be her name?" (Genesis 17:15).
Allegorical Interpretation of Genesis
[217] On the other hand, you will find virtue full of exceeding joy at her pregnancy, and the good man begetting with laughter and a glad heart, and the offspring of them both laughter itself. That the wise man begets with joy not sorrow, the Divine word shall testify in these words, “God said to Abraham, Sarai thy wife shall not be called Sarai, but Sarah shall be her name: I will bless her and will give thee a child of her” (Gen. 17:15 f.); then he says further, “And Abraham fell on his face and laughed and said, Shall he that is a hundred years old have a son, and shall Sarah who is ninety years old bear?” (ibid. 17).