(25:19) These are the offspring of Isaac son of Abraham. Abraham was Isaac's father.
Abraham was Isaac's father This phrase seems to be redundant, because [the verse] already says “Isaac son of Abraham.” Why the repetition? When Sarah gave birth to Isaac, people made fun of Abraham, saying, “Could Abraham father a child at the age of one hundred?” Immediately, Isaac's facial features changed, and he came to look exactly like Abraham. Seeing this, they all cried out, “Abraham is Isaac's father!” (Bava Metzia 87a).
(25:21) Isaac pleaded with God opposite his wife, because she was barren. God granted his plea, and Rebeccah became pregnant.
opposite his wife It does not say “concerning his wife” but “opposite his wife.” From here we see that both Rebeccah and Isaac were infertile, and both Isaac and Rebeccah prayed to be healed from their condition. And why is it that our forefathers were incapable of having children? Said R. Yitzchak: God yearns to hear the prayers of the righteous; that's why He withholds