Rabbi Chiya talks about Moses' rod that was turned into a snake, and the verse, "The way of a snake upon a rock." He says that the rock is Malchut, and the rock is God. Rock always refers to Gvurah, so that when God wants to punish, Gvurah is aroused and punishes. The flow of water in "And you shall smite the rock, and there shall come water out of it" is the flow of Gvurah from the higher to the lower levels, drawn by the Holy Name of God engraved on the rod. Rabbi Aba says there is a supernal Rock and a lower rock that emerges from it. He tells us that wherever 'water' is written it refers to the light of Chesed; it is the sign and miracle of the Holy One, blessed be He that the rock, which is judgment, should inspire the flowing forth of Chassadim. Rabbi Shimon turns to the scripture, "He is the rock, His work is perfect," saying that the rock here is Abraham, who is Chesed. The sins of Yisrael weakened the rock from what it had been originally.