Tertullian

For Joshua was to lead the people into the land of promise, not Moses. Now he called him an "angel," on account of the magnitude of the mighty deeds that he was to achieve (which mighty deeds Joshua the son of Nun did, and you yourselves have read about) and on account of his office of prophet announcing the divine will. Just as the Spirit, speaking in the person of the Father, calls the forerunner of Christ, John, a future "angel," through the prophet: "Behold, I sent my angel before your"—that is, Christ's—"face, who shall prepare your way before you." Nor is it a novel practice to the Holy Spirit to call those "angels" whom God has appointed as ministers of his power. For the same John is called not merely an "angel" of Christ but also a "lamp" shining before Christ. For David predicts, "I have prepared the lamp for my Christ"; and so Christ, coming "to fulfill the prophets," referred to him [John] [when speaking] to the Jews. "He was," he says, "the burning and shining lamp," being the one who not only prepared his ways in the desert" but, by pointing out "the Lamb of God," enlightened the minds of people by his proclaiming, so that they understood him to be that Lamb whom Moses was accustomed to announce as destined to suffer.