Matthew 4:12

Now when he heard (akousa de). The reason for Christ's return to Galilee is given here to be that John had been delivered up into prison. The Synoptic Gospels skip from the temptation of Jesus to the Galilean ministry, a whole year. But for John 1:19-3:36 we should know nothing of the "year of obscurity" (Stalker). John supplies items to help fill in the picture. Christ's work in Galilee began after the close of the active ministry of the Baptist who lingered on in prison for a year or more.