You have asked about this statement from John 11:25: "I am the resurrection and the life; he who believes in me, though he die, yet shall he live." Jesus is speaking to his friend Martha, whose brother Lazarus has just died. She has, in her grief, gently accused Jesus, saying "If you had been here, my brother would not have died" (Jn. 11:21).
I believe this is a key moment in the ministry of Jesus Christ; I believe it is the moment when he realizes that in order to achieve his spiritual purpose of awakening others to the Christ Presence within them, he will have to move beyond his own human expression. And because he loved his life and the people with whom he was sharing it, we're told shortly after that "Jesus wept" (Jn. 11:35).
Jesus was never about claiming unique powers for himself, but about demonstrating the spiritual powers inherent in each person. Those powers—divine attributes —are what he called the Christ, and it is as the Christ that this statement must be understood. "I am" is the identity of God that Moses is given before the burning bush in Exodus 3:14: "I AM that I AM. Say this to the people of Israel: I AM has sent me to you." In other words, you do not need authority from a God on high. It is the Presence of God indwelling each of us as the Christ that is the Source of all good and all spiritual guidance.
Jesus is saying here to Martha that the Christ is a Power of infinite life. As the Christ we do not ever die; we are spiritual beings, as eternal as our divine Source. When we truly know and embrace the Christ—the I AM of our being—then although our physical forms may age and fade, our true identity will never die, never end. And shortly after this scene, Jesus proceeds to demonstrate this truth by making his own departure from human form a great lesson for us all.