John's role evokes Malachi 3:1, Malachi 4:5-6, and Isaiah 40:3, where a messenger prepares for God's coming.
Luke's narrative makes Jesus the one immediately preceded by John. This creates a striking correspondence between the promised coming of the Lord and the arrival of Jesus.
The argument rests on Luke's narrative use of YHWH texts, not on a bare title. It is strong evidence that Jesus is included in the divine visitation anticipated by Scripture.