TT #3 · Parashas Toldos · Passuk 25:21
Yitzchak pleaded with Hashem on behalf of his wife, because she was infertile; and Hashem responded to his plea, and his wife Rivkah conceived.
Torah Temimah points to Yevamos 64a. E-Daf · Sefaria — Yevamos 64a
It does not say “for his wife” but “opposite his wife,” teaching that both of them were barren… because the Holy One desires the prayers of the righteous.
Custom (Bavli — both were barren; God desires the prayers of the righteous)
Both Yitzchak and Rivkah were barren; the purpose of their barrenness was that the Holy One desires the prayers of the righteous.