Repent and Believe
In tomorrow's Gospel reading, Jesus begins his ministry by preaching, "The time is fulfilled, and the kingdom of God has come near; repent, and believe in the good news."
One commentary on this passage notes:
Both John the Baptist and Jesus preach the need for repentance, but the significance of, and occasion for, repentance is different for each.—from Living Liturgy: Spirituality, Celebration, and Catechesis for Sundays and Solemnities Year B - 2006, p. 43.
Earlier in Mark's gospel John the Baptist had preached a "baptism of repentance for the forgiveness of sins" (1:4; see Second Sunday of Advent). Such repentance was a prerequisite for forgiveness and thus a way to escape impending judgment.
While Jesus, too, preaches repentance, the significance is different: repentance is linked to believing the gospel. The good news that Jesus announces requires a response, not of purification, but of believing.
At the same time, the occasion for repentance as preached by John and Jesus is also different. For John the urgent need to repent is linked to the imminent coming of "one mightier than I" (1:7). Now that the Mightier One, that is, Jesus, has appeared, repentance is needed because "the kingdom of God is at hand."
In the Old Testament the prophet Isaiah announced the "good news" that "your God is King"; God, in turn announces, "Here I am" and his arrival ushers in a time of "peace . . .[and] salvation" (Isa 57:6-7). This passage from Isaiah brings together key elements of Jesus' own announcement: good news, God's reign as king, and the nearness of God's rule.
Thus, Jesus is fulfilling that ancient prophecy and in him the kingdom of God is being made manifest. But because Jesus is an itinerant preacher and the son of a carpenter, it would have been unexpected to see in him the glorious approach of God's kingdom. In this context, "repent" means a change of mind: people would need to adjust their expectations as to how it is that God is working in the world.