וַיֶּעְתַּ֨ר יִצְחָ֤ק לַֽיהוָה֙ לְנֹ֣כַח אִשְׁתּ֔וֹ כִּ֥י עֲקָרָ֖ה הִ֑וא וַיֵּעָ֤תֶר לוֹ֙ יְהוָ֔ה וַתַּ֖הַר רִבְקָ֥ה אִשְׁתּֽוֹ׃
And Isaac entreated the LORD for his wife, because she was barren; and the LORD let Himself be entreated of him, and Rebekah his wife conceived.
Read halakhic rulings (Jewish law) on Genesis 25:21: and classical halakhic sources.