Peter asked Jesus, "Lord, whither goest thou?"
Jesus explained that he couldn't follow Him now.
but that he would follow him later.

Peter couldn't understand why he couldn't follow
Him then, so he said, "I will lay down my life for
thy sake."

Jesus could have told Peter why, but instead He
told him that when the cock crowed he would
have denied Him three times.

Peter didn't realize what events were at work
to catch him and show him how weak he was.