I remember settling a bar discussion among friends about who was the first Christian. There had been much dispute and debate had settled into two camps: John the Baptist or Jesus.
Well, Jesus knew he was Lord, so there was no need of faith in that matter, and John the Baptist didn't learn of Jesus until later in life. It had to be Mary, at the Annunciation, when she agreed to bear the Son of God....that was the first moment anyone on earth believed that Jesus was Christ, the Son of God, Lord and Savior.
Of course it was Mary, it was agreed.
As it happened, the dispute ended, and discussion turned to arguments about something else entire.