The messenger sent ahead
Jesus identified John the Baptist as the promised messenger sent ahead to prepare the way, using wording drawn from Malachi.
“Behold, I will send My messenger, who will prepare the way before Me. Then the Lord whom you seek will suddenly come to His temple—the Messenger of the covenant, in whom you delight—see, He is coming,” says the LORD of Hosts.
Malachi 3:1 promises that God will send His messenger to prepare the way; in Matthew 11:10 Jesus uses the same promise and says that John is the one about whom it was written.