The Gospel of Mark introduces John as a fulfillment of a prophecy from the Book of Isaiah (in fact, a conflation of texts from Isaiah, Malachi and Exodus) about a messenger being sent ahead, and a voice crying out in the wilderness. John is described as wearing clothes of camel's hair, living on locusts and wild honey. John proclaims baptism of repentance for the forgiveness of sin, and says another will come after him who will not baptize with water, but with the Holy Spirit.