“And he said, ‘Am I in the place of God, who has withheld from you the fruit of the womb?’” RASHI interpreted, “You say that I should do as father; I am not as father. Father had no sons; I have sons from you and not from him (VaYetze).
We found a prayer with Isaac, as it is written, “And Isaac pleaded with the Lord on behalf of his wife, for she was barren.” This is why it is written “on behalf of his wife,” and not “on behalf of Rebecca,” since it is not the manner of the righteous to pray that the Creator will change the ways of nature in their favor. Thus, according to the interpretation of The Zohar, Jacob could not pray for her.