The sight must have penetrated John's mind. He realized what had happened. He saw and believed. Later all the apostles would understand from scripture that Jesus had predicted His resurrection but, for now, John believed because he saw. Here, then, is a great lesson.
Love is a great interpreter.
The Lord gave John the eyes to read the signs and a mind to understand. There was a great bond between Jesus and John for John was the apostle Jesus loved. Love can grasp the truth when intellect is left groping. Let us love Jesus with our whole hearts, minds, and souls.