Zera Kodesh

Another interpretation: "And Yitzchak entreated," etc. It is written in the books that when a person prays, the Shechinah (the Divine Presence) stands opposite him and says after him every single word, literally. Certainly this is so only when he prays properly, without extraneous thoughts or ulterior motives. This is the meaning of "And Yitzchak entreated Hashem opposite his wife": the Shechinah is called a woman (wife). When Yitzchak prayed, he prayed opposite the Shechinah, who prayed every word together with him.

Another interpretation, in the manner of the above: Yitzchak prayed not for his own need but for the tikkun (repair) of the Shechinah, that she should have no suffering, as above. "And Yitzchak entreated Hashem" means that there should be no suffering for Him, may He be blessed. Now, they said: "From where do we know that HaKadosh Baruch Hu (the Holy One, blessed be He) prays?" etc. And He prayed on Yitzchak's behalf, for Yitzchak's need, that he beget children. This is the meaning of "And Hashem was entreated by him": He, may He be blessed, prayed for him. "And Rivkah his wife conceived," etc. Also in line with what our Sages, of blessed memory, said: "One who prays for his fellow is answered first." All the more so one who prays for Him, may He be blessed, as above, for Yitzchak prayed for His need. Therefore Yitzchak was answered regarding his own need, "and Rivkah his wife conceived," etc.