Kabbalah su Genesi 15:3

Come and behold, Abraham did not pray before the Holy One, blessed be He, so that He would give him sons, even though Sarah was barren. And although it may be said that he prayed, saying, "Behold, to me You gave no seed," (Gen. 15:3) it is not a prayer, but simply a statement to his Master. But Isaac prayed for his wife because he knew that his wife, and not he, was sterile. And although Isaac knew by the inner meaning of wisdom that Jacob was bound to come from him and produce the twelve tribes, he did not know whether this would be from this wife or from another. Therefore the scripture reads, "for his wife" (Gen. 25:21), and not specifically "for Rivkah."