How many times does the Bible mention Angel Gabriel’s appearance?
While I, Daniel, sought the meaning of the vision I had seen, one who looked like a man stood before me, and on the Ulai I heard a human voice that cried out, “Gabriel, explain the vision to this man.” When he came near where I was standing, I fell prostrate in terror. But he said to me, “Understand, O son of man, that the vision refers to the end time.”
I was still praying to the Lord, my God, confessing my sin and the sin of my people Israel, presenting my petition concerning the holy mountain of my God—I was still praying, when the man, Gabriel, whom I had seen in vision before, came to me in flight at the time of the evening offering. He instructed me in these words: “Daniel, I have now come to give you understanding.”
Then Zechariah said to the angel, “How shall I know this? For I am an old man, and my wife is advanced in years.” And the angel said to him in reply, “I am Gabriel, who stand before God. I was sent to speak to you and to announce to you this good news. But now you will be speechless and unable to talk until the day these things take place, because you did not believe my words, which will be fulfilled at their proper time.”
In the sixth month, the angel Gabriel was sent from God to a town of Galilee called Nazareth, to a virgin betrothed to a man named Joseph, of the house of David, and the virgin’s name was Mary.
New Advent Catholic Encyclopaedia says:
As remarked above, Gabriel is mentioned only twice in the New Testament, but it is not unreasonable to suppose with Christian tradition that it is he who appeared to St. Joseph and to the shepherds, and also that it was he who “strengthened” Our Lord in the garden (cf. the Hymn for Lauds on 24 March). Gabriel is generally termed only an archangel, but the expression used by St. Raphael, “I am the angel Raphael, one of the seven, who stand before the Lord” (Tobit 12:15) and St. Gabriel’s own words, “I am Gabriel, who stand before God” (Luke 1:19), have led some to think that these angels must belong to the highest rank; but this is generally explained as referring to their rank as the highest of God’s messengers, and not as placing them among the Seraphim and Cherubim (cf. St. Thomas, I.112.3; III.30.2 ad 4um).