Matthew 21:21 allegory. What mountain should go jump in what sea?

At times mountains represent obstacles. For example, the obstacles that stood in the way of Israel’s returning from Babylonian exile and those that later prevented progress in the temple rebuilding work were compared to mountains. (Isa 40:1-4; Zec 4:7) Faith can move similar mountainous obstacles and, if it be God’s will, even literal mountains.—Mt 17:20; 21:21; Mr 11:23; 1Co 13:2.