Yea, while I was speaking in prayer, even the man Gabriel, whom I had seen in the vision at the beginning, being caused to fly swiftly, reached me about the time of the evening offering.
All Commentaries on Daniel 9:21 Go To Daniel 9
Jerome
AD 420
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.