Why was this moment where Jesus talked to the prophets of old so necessary? This could be a really long writing if we're going to answer all of that question. Here's one piece of that picture: because Moses and Elijah represented to law and the prophets, and Jesus represented the fulfillment of both. When the apostles look up after being knocked to the ground, they see only him. This didn't mean that the law and the prophets disappear when Jesus shows up. It means that his life brings them to fruition. His example shows what they look like in action, not just rules to point to our wrongs or hopeful things to happen in the future. It was all coming true in Jesus.