We know that Joseph was a poor man because of the offering he gave at the temple when Jesus was born. So in this place of obscurity and poverty Jesus lived, unknown, unrecognised. He knew who he was and why he had come into the world. What a secret to have to keep! But then one day, as Oswald Sanders pictures it, Jesus shut the carpenter’s day for the last time. He walked from Nazareth to the desert of Judea, and at his baptism the secret was revealed.
God the Father tore the heavens open (a picture of eagerness) to announce that he was well-pleased with the life his Son lived in obscure Nazareth. There in Nazareth had lived One who for thirty years had perfectly kept the law of God in heart, mind and action. A perfect life, unknown to earth, but known in heaven.
This secret obedience not only revealed his personal devotion to God, it was part of the salvation he was working out for his people. We have failed to keep the law of God and have to suffer the penalty. To be redeemed from that penalty two things are required: (1) the payment of the penalty, which was paid on the cross; (2) a perfect keeping of the law, which also was done for us by Jesus, and mostly done for us in Nazareth.
So his baptism was the occasion of the Father saying how much he loved the hidden years.