Genesis 25:21

“And Isaac entreated the Lord for his wife, etc.] Was very earnest and constant in his supplications for her, as the word signifies, as is observed by Jarchi; or, “before his wife” f1392, she being present, and joining with him in his prayers: the reason was, because she [was] barren; which appeared by the length of time they had been married, which was near twenty years, (see <012526>Genesis 25:26). The Jewish writers f1393 say, that, after twenty years, Isaac took her and went with her to Mount Moriah, to the place where he was bound, and prayed that she might conceive; putting the Lord in mind of the promise he there made of the multiplication of Abraham’s seed, (<012217>Genesis 22:17,18):…”

“Isaac entreated the Lord for his wife--Though tried in a similar way to his father, he did not follow the same crooked policy. Twenty years he continued unblessed with offspring, whose seed was to be "as the stars" [Gen 26:4]. But in answer to their mutual prayers (Pe1 3:7), Rebekah was divinely informed that she was to be the mother of twins, who should be the progenitors of two independent nations; that the descendants of the younger should be the more powerful and subdue those of the other (Rom 9:12; Ch2 21:8).”

“25:21 For twenty years, Rebekah was barren (cp. 25:20, 26), like Sarah (see 16:1). This condition tested their faith (see study note on 16:1-3). How could they be childless when God promised that nations would issue from them? • Isaac pleaded with the Lord and the Lord answered Isaac’s prayer. Isaac apparently learned from his father’s mistake and responded in faith.”