John 8:58-59 Jesus said to them, “Truly, truly, I say to you, before Abraham was, I am.” So they picked up stones to throw at him, but Jesus hid himself and went out of the temple.
John Piper, in a sermon, “Death Is Not the End of Life,” explained,
“Now, if Jesus had meant to say it like a good Jehovah’s witness, he would’ve said, “I pre-existed Abraham,” he could have said that real easily. “Before Abraham was, I was.” That’s the way you say that, right? Before Abraham was, I was — like Michael, an angel. There’s no blasphemy in angels showing up in human flesh. That’s what they do. They take on appearances. There’s no blasphemy in an angel showing up. This is blasphemy and that’s true. They were ready to kill him and you kill blasphemers by stoning.
The reason they were ready to kill him is that he didn’t say, “Before Abraham was, I was.” He said, “Before Abraham was, I am,” which is weird — weird grammar and he means it to be gloriously weird. He knew what they knew — Exodus 3:14. “Who shall I say sent me,” Moses asks God. When I go down there, they’re going to say, “Who sent you?” He said, “Tell them I am who I am. Say I am sent you.” This is the clearest declaration in the mouth of Jesus that he is God. That he is Yahweh, the God of the Old Testament. “I am.”