English: It does not say “for his wife” but “opposite his wife,” teaching that both of them were barren… because the Holy One, blessed be He, desires the prayers of the righteous.
On the daf / in context: The wording “le-nochach ishto” implies that both Yitzchak and Rivkah were infertile; the barrenness itself was arranged so that they would pray.
Type of Learning
Custom (Bavli — both were barren; God desires the prayers of the righteous)
What Is Learned
Both Yitzchak and Rivkah were barren; the language “opposite his wife” teaches this, and the purpose of their barrenness was that the Holy One desires the prayers of the righteous.