"And Abram and Nahor took for themselves wives" (Genesis 11:29). Abram was greater than Nahor by a year, and Nahor was greater than Haran by a year. And it is written, "And Abram and Nahor took for themselves wives," and so forth. And Rabbi Yitzchak said: Iscah is Sarah. And why was she called Iscah? Because she gazed [sokhah] with the Holy Spirit. And this is what is written, "All that Sarah says to you, listen to her voice" (Genesis 21:12).
Iscah Is Sarah Who Gazed With the Holy Spirit
Yalkut Shimoni on Torah 62:15
(בראשית יא כט) וַיִּקַּח אַבְרָם וְנָחוֹר לָהֶם נָשִׁים. אַבְרָם גָּדוֹל מִנָּחוֹר שָׁנָה נָחוֹר גָּדוֹל מֵהָרָן שָׁנָה וּכְתִיב וַיִּקַּח אַבְרָם וְנָחוֹר לָהֶם נָשִׁים וְגוֹ' וְאָמַר רַבִּי יִצְחָק, יִסְכָּה זוֹ שָׂרָה, וְלָמָּה נִקְרָא שְׁמָהּ יִסְכָּה, שֶׁסּוֹכָה בְּרוּחַ הַקֹּדֶשׁ, וְהַיְינוּ דִּכְתִיב (בראשית כא, יב) "כָּל אֲשֶׁר תֹּאמַר אֵלֶיךָ שָׂרָה שְׁמַע בְּקֹלָהּ".