David lifts his eyes to the mountains and prays — "A song of ascents" — and God answers him through a text he might not have expected: Moses's blessing of Judah. "And this is the blessing for Judah... Hear, Lord, the voice of Judah; bring him to his people" (Deuteronomy 33:7). The midrash understands this verse as Moses praying on behalf of all future kings of Judah — not just the tribe, but David specifically, and his descendants.
David's prayer is heard because it stands in a line of prayers that goes back to the wilderness. Moses prayed at Sinai for Judah's future. David prays in Jerusalem for his present. The psalm records both — the God who heard Moses at Sinai hears David on the slope, descending toward battle. The continuity of divine attention is the midrash's argument: the same God who formed the covenant at the beginning is present at every subsequent moment of crisis.
The midrash notes that David prayed going down a slope — at his most vulnerable, on his way to a battlefield. Not in the Temple, not in a moment of victory, but descending. The rabbis saw this as the ideal posture for prayer: not from a position of strength, but from the moment of greatest need. "From my distress I called to God; He answered me" (Psalm 118:5). The prayer that goes up from the bottom of the slope reaches the top of heaven.