The voice preparing the way
Each Gospel connects John the Baptist with Isaiah's voice in the wilderness preparing the way of the Lord.
A voice of one calling: “Prepare the way for the LORD in the wilderness; make a straight highway for our God in the desert. Every valley shall be lifted up, and every mountain and hill made low; the uneven ground will become smooth, and the rugged land a plain. And the glory of the LORD will be revealed, and all humanity together will see it. For the mouth of the LORD has spoken.”
Matthew 3:3, Mark 1:2-3, and Luke 3:4-6 quote Isaiah in introducing John's ministry, while John 1:23 records John applying Isaiah's words to himself.