Matthew 3:6 describes the general baptism of repentance that John performed, which Jesus came to participate in.

Matthew 2:22 explains why Jesus was in Galilee (return from Egypt, avoiding Archelaus) — the starting point for his journey to the Jordan.

Mark 1:9 gives a nearly identical account of Jesus coming from Nazareth to be baptized by John.

John 1:15 records John's earlier testimony about Jesus being before him, directly connecting to Jesus' arrival.

John 1:33 reveals that John recognized Jesus as the one who would baptize with the Holy Spirit at his baptism.

Luke 3:21 adds that Jesus was praying after his baptism, a detail not in Matthew.