Mark 1:2-4

just as the prophet Isaiah had written: “Look, I am sending my messenger ahead of you, and he will prepare your way. He is a voice shouting in the wilderness, ‘Prepare the way for the LORD’s coming! Clear the road for him!’” This messenger was John the Baptist. He was in the wilderness and preached that people should be baptized to show that they had repented of their sins and turned to God to be forgiven.