The following is an excerpt from
The MacArthur New Testament Commentary on John 8.
Jesus said to them, “Truly, truly, I say to you, before Abraham was born, I am.” (8:58)
Jesus’ climactic reply, “Truly, truly, I say to you, before Abraham was born, I am,” was nothing less than a claim to full deity. The Lord once again took for Himself the sacred name of God (see the discussion of 8:24 in chapter 29 of this volume). Obviously, as the eternal God (John 1:1–2), He existed before Abraham’s time. Homer Kent explains, “By using the timeless ‘I am’ rather than ‘I was,’ Jesus conveyed not only the idea of existence prior to Abraham, but timelessness—the very nature of God himself (Exod. 3:14)” (Light in the Darkness [Grand Rapids: Baker, 1974], 128–29).