Twenty years of marriage and no child. Targum Pseudo-Jonathan on Genesis 25:21 says Isaac did not pray in his tent, did not pray in his field, did not pray at the local altar. He went up to the mountain — "the mountain of worship, the place where his father had bound him."
Moriah. The Akedah. The place where, decades earlier, Isaac had been laid on an altar by Abraham's own hand and then spared by an angel's voice (Genesis 22). Now he is back. Same mountain. Same stones. Different grief.
The Targum uses a striking phrase about the prayer: Isaac "turned the attention of the Holy One, blessed be He, from that which He had decreed concerning him who had been childless." He turned the attention. The Aramaic verb is almost physical — a bending of heaven's gaze. The decree against him was real. The decree was overturned by prayer on the spot where he had once been offered.
There is a principle the sages will draw from this verse: tefillah mevatelet ha-gezerah, prayer annuls the decree (Rosh Hashanah 16b). And the reason it works here, the tradition says, is the place. The stones of Moriah remembered Isaac. Every prayer spoken on that mountain rested on the merit of the one who had been bound there. He was praying with his own past as his most powerful ally.
The closing of the verse is quiet triumph: "And he was enlarged, and Rebekah his wife was with child." Enlarged — the Aramaic suggests an expansion, a widening. Isaac's prayer did not just get an answer. It enlarged him. The man who returned to the mountain came back bigger than the man who climbed it.