"I will not break my covenant, nor change that which has come out of my lips" (Psalm 89:35). The binding of Isaac begins with this verse in Aggadat Bereshit — not with the command itself, not with Abraham's early rising, but with God's promise that the covenant would survive whatever was about to happen.
When Abraham raised the knife, the angels wept. Isaiah records it: "Their mighty men cry out without, the messengers of peace weep bitterly" (Isaiah 33:7). The angels could not interfere — they had no authority here — but they were not unmoved. Heaven watched. Heaven grieved. The rabbis wanted this known: the test of the Binding was not observed coldly from above. The very beings who execute divine will stood at the edge of the moment and wept.
God stopped Abraham's hand and showed him the ram. "Now I know that you are a God-fearing man" (Genesis 22:12). The rabbis puzzled over this — did God not always know? Their answer: God knew in the abstract. The test made it real, recorded in time, available to all future generations as evidence. Abraham's willingness is now in the record forever. Every generation that needs to invoke it can point to Moriah and say: this is what covenant looks like. Not comfortable. Not theoretical. This.