Midrash for Yevamot 127:9

א"ר יצחק מפני מה היו אבותינו עקורים מפני שהקב"ה מתאוה לתפלתן של צדיקים א"ר יצחק למה נמשלה תפלתן של צדיקים כעתר מה עתר זה מהפך התבואה ממקום למקום כך תפלתן של צדיקים מהפכת מדותיו של הקב"ה ממדת רגזנות למדת רחמנות אמר רבי אמי אברהם ושרה טומטמין היו שנאמר (ישעיהו נא, א) הביטו אל צור

his wife.<span class="x" onmousemove="('comment',' Gen. XXV, 21. ');">²³</span> It does not say 'for his wife' but opposite. This teaches that both were barren.<span class="x" onmousemove="('comment',' He had to pray not only for her but for himself also. ');">²⁴</span> If so, And the Lord let Himself be entreated of him<span class="x" onmousemove="('comment',' Gen. XXV, 21. ');">²³</span> should have read, And the Lord let Himself be entreated of them!<span class="x" onmousemove="('comment',' Since Isaac's prayer was not on behalf of his wife only but on behalf of himself as well. ');">²⁵</span> — Because the prayer of a righteous man the son of a righteous man is not like the prayer of a righteous man the son of a wicked man.<span class="x" onmousemove="('comment',' Rebekah's father, Bethuel, was a wicked man. The implication of 'him' in 'entreated of him' is that Isaac's prayer was accepted before Rebekah's. ');">²⁶</span> R. Isaac stated: Why were our ancestors barren? — Because the Holy One, blessed be He, longs to hear the prayer of the righteous. R. Isaac further stated: Why is the prayer of the righteous compared to a pitchfork?<span class="x" onmousemove="('comment',' [H] or [H] of the same rt. as [H] and he entreated. ');">²⁷</span> As a pitchfork turns the sheaves of grain from one position to another, so does the prayer of the righteous turn the dispensations of the Holy One, blessed be He, from the attribute of anger to the attribute of mercy. R. Ammi stated: Abraham and Sarah were originally of doubtful sex;<span class="x" onmousemove="('comment',' [H], Glos, s.v. tumtum. ');">²⁸</span> for it is said, Look unto to the rock

Ein Yaakov (Glick Edition)