When did Jesus first introduce himself as Son of God?

We read in Mtt 16:13-16: > When Jesus came to the region of Caesarea Philippi, he asked his disciples, “Who do people say the Son of Man is?” They replied, “Some say John the Baptist; others say Elijah; and still others, Jeremiah or one of the prophets.” “But what about you?” he asked. “Who do you say I am?” Simon Peter answered, “You are the Messiah, the Son of the living God.”. It is usual for people entering public life to introduce themselves , or to get the introduction done by someone else. We see John the Baptist introducing Jesus as the Lamb of God (Jn 1:29). We also see Jesus reading from Isiah and introducing himself as the Anointed One ( Lk 4:21). But Mtt 16 suggests that it was Peter who first acknowledged Jesus as Son of God, before which he had been known to the public by other attributes. My question therefore is : When did Jesus first introduce himself as Son of God ?