Only after three years (or in the third year): This could be three years after Paul became a follower of Jesus or three years after his return from Arabia. This event is likely the visit mentioned in Acts 9:26–30.
to confer with Cephas (Peter): Peter had something Paul did not—personal experience with Jesus during his time on Earth.
Paul spent fifteen days with Peter. This was not enough time for Peter to become Paul's teacher, but it gave them enough time to talk carefully about what they were teaching people about Jesus.