In John 8:58, declares that He is the great I AM, the same term that Yahweh uses for Himself in Exodus 3:14.
Let’s take Yeshua’s claim in its context. He is arguing with the Pharisees and says (some sentences omitted and paraphrased for brevity):
Yeshua: Truly, truly, I say unto you, if a man keep my saying, he shall never see death.
Pharisees: Abraham is dead, and you say If a man keep my saying, he shall never taste death. Are you greater than Abraham, who is dead? And the prophets are dead: who do you make yourself out to be?
Jesus : It is my father who honors me – but you have not known him. Your father Abraham rejoiced to see my day: and he saw it, and was glad.
Pharisees: You are not yet fifty years old, and you have seen Abraham?
Jesus: Truly, truly, I say to you, before Abraham was, I am.
Then they took up stones to throw at him, but Yeshua hid himself.
By saying that before Abraham was, “I Am”, just is equating himself with the great I Am of Exodus 3:13-14:
They shall say to me “What is his name? What shall I say to them?
And God said to Moses, I AM THAT I AM: and he said Thus shall you say unot the children of Israel, I AM has sent me unto you.
Not only was Yeshua equating himself with Yahweh, but he was doing it in the context of time; the pharisees challenged him that he was not yet fifty, but his answer indicates that he existed prior to Abraham – thus a pre-existent Yeshua, prior to the incarnation, is being claimed here. This context is important, and the Pharisees obviously understood what he was claiming; that He not only was God, but that he pre-existed – which they considered blasphemy, thus they picked up stones to stone him.
For more insight into this phrase “I Am” (Ego Eimi), check out this link.