Ambrose of Milan — as excerpted in the Catena Aurea on Luke 3:1-2

“The Son of God being about to gather together the Church, commences His work in His servant. And so it is well said, The word of the Lord came to John, that the Church should begin not from man, but from the Word. But Luke, in order to declare that John was a prophet, rightly used these few words, The word of the Lord came to him. He adds nothing else, for they need not their own judgment who are filled with the Word of God. By saying this one thing, he has therefore declared all. But Matthew and Mark desired to shew him to be a prophet, by his raiment, his girdle, and his food.”