1 Peter 2:21

To this you were called, because Christ suffered for us, leaving us an example, that you should follow His steps.

Peter was a witness to the life of Jesus and saw all that He suffered and went through.  That is why Peter can say that Jesus is an example of how we can overcome in the world.  Peter followed the example of Jesus doing the works of Jesus on this earth.  We have been called to follow in the footstep of Christ and overcome the devil just as Jesus overcame.