Daniel 9:21

Let them read Daniel, saying, "Behold the man Gabriel." But why do we delay any longer to stop their mouths by another most clear and most weighty proof, where not an angel in the singular nor men in the plural are spoken of, but simply angels; by whom not any particular word was wrought, but the Law itself is most distinctly declared to be given; which certainly none of the faithful doubts that God gave to Moses for the control of the children of Israel, or yet, that it was given by angels. So Stephen speaks: "Ye stiff-necked," he says, "and uncircumcised in heart and ears, ye do always resist the Holy Ghost: as your fathers did, so do ye. Which of the prophets have not your fathers persecuted? and they have slain them which showed before of the coming of the Just One; of whom ye have been now the betrayers and murderers: who have received the Law by the disposition of angels, and have not kept it." What is more evident than this? What more strong than such an authority? The Law, indeed, was given to that people by the disposition of angels; but the advent of our Lord Jesus Christ was by it prepared and pre-announced; and He Himself, as the Word of God, was in some wonderful and unspeakable manner in the angels, by whose disposition the Law itself was given. And hence He said in the Gospel, "For had ye believed Moses, ye would have believed me; for he wrote of me." Therefore then the Lord was speaking by the angels; and the son of God, who was to be the Mediator of God and men, from the seed of Abraham, was preparing His own advent by the angels, that He might find some by whom He would be received, confessing themselves guilty, whom the Law unfulfilled had made transgressors.

And so confessing from the face of the people, he describes these things, declaring the sins of the people and of their fathers, who did not obey his slaves the prophets, who were sent to them to speak in the name of the Lord. And when he was proclaiming every supplication in humility and fastings and sackcloth, the angel Gabriel was sent forth to him, in order to cause him to understand what was sought by him. For Daniel speaks in this way, "And while I was still speaking and praying and declaring my sins and the sins of my people, prostrating my pitiful case before the Lord my God concerning the holy Mountain, and while I was still speaking in prayer, behold, the man Gabriel, whom I saw in the vision in the beginning, came flying and he touched me around the evening sacrifice and he caused me to understand and spoke with me and said, 'Daniel, now I have come to teach you understanding. In the beginning of your supplication the word went out and I myself came to proclaim to you that you are cherished man.'" [Daniel 9:20-23]

This was the evening fast, which offers a richer prayer to God, since it takes place with fasting during the evening.

Verse 21. "While I was still speaking in my prayer, behold the man Gabriel, whom I had seen at the beginning of the vision." He calls the previous vision preceding this one the beginning. The effect of his prayer was considerable, and the promise of God was fulfilled which says, "While thou art yet speaking, lo, I am at hand" (Isaiah 58:9). And Gabriel appears not as an angel or archangel, but as a man (vir), a term used to indicate the quality of virtue rather than specifying his sex. "...he quickly flew to me and touched me at the time of the evening sacrifice." It is stated that he flew, because he had made his appearance as a man. It is said that it was at the time of the evening sacrifice, in order to show that the prophet's prayer had persisted from the morning sacrifice even unto the evening sacrifice, and that God for that reason directed His mercy towards him.

See how the prophet likened the swiftness of angels to winged flight, on account of the nimbleness and the lightness of the weight of the angels, who are spirits flying quickly to obey what is commanded as Solomon says, "Do not curse your king in an oath lest a winged bird carries your words to him." [Ecclesiastes 10:20]