Your father Abraham rejoiced that he would see my day. He saw it and was glad. So the Jews said to him, You are not yet fifty years old, and have you seen Abraham? 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 8:56-9
As I told the Jehovah’s Witnesses at the door yesterday, the Jews knew what Jesus was claiming here. He is God the Son. And the Holy Spirit is a person. And the word “Trinity” is simply theological shorthand for truths revealed repeatedly in both the Old and New Testaments.
Opportunities at your door like this are a convicting reminder to always be “prepared to make a defense to anyone who asks you for a reason for the hope that is in you” (1 Peter 3:15 ESV).