Theophylact of Ohrid — as excerpted in the Catena Aurea on Mark 1:2-3

“The Forerunner of Christ, therefore, is called an angel, on account of his angelic life and lofty reverence. Again, where he says, Before thy face, it is as if he said, Thy messenger is near thee: whence is shewn the intimate connection of the Forerunner with Christ; for those walk next to kings, who are their greatest friends. There follows, Who will prepare thy way before thee. For by baptism he prepared the minds of the Jews to receive Christ.”