Although Mark's Gospel implies that the arrival of John the Baptist is the fulfilment of a prophecy from the Book of Isaiah, the words quoted ("I will send my messenger ahead of you, who will prepare your way – a voice of one calling in the wilderness, 'Prepare the way for the Lord, make straight paths for him.'") are actually a composite of texts from Isaiah, Malachi and the Book of Exodus. (Matthew and Luke drop the first part of the reference.)