King Benjamin declared that "glad tidings of great joy" had been communicated to him by an angel of the Lord. (Mosiah 3:3; see also Helaman 13:7) However, the identify of this angel is not revealed. According to Rodney Turner, since no one was yet resurrected the angel was probably a translated being. I am tempted to suggest Enoch but this is sheer conjecture on my part. . . . Insofar as extant scripture is concerned, this angel was the first to speak of Christ as the Lord God Omnipotent. This title appears nowhere in the standard works other than in chapters 3 and 5 of Mosiah, and in Revelation 19:6. [Rodney Turner, "The Great Conversion," in Studies in Scripture: Book of Mormon, Part 1, pp. 214, 228]
“Glad Tidings of Great Joy”
Benjamin declared that:
"the things which I shall tell you are made known unto me by an angel from God. And he said unto me: Awake; and I awoke, and behold he stood before me. And he said unto Me: Awake, and hear the words which I shall tell thee; for behold, I am come to declare unto you the glad tidings of great joy. (Mosiah 3:2-3)
According to Hugh Nibley, this phrase "glad tidings of great joy" is very interesting. . . . The angel uses this on more than one occasion. It's always an angel that says this, "glad tidings of great joy" and the angel uses this phrase on more than one occasion. Take, for example, the reference Alma the younger makes in his preaching at Ammonihah:
Yea, and the voice of the Lord, by the mouth of angels, doth declare it unto all nations; yea, doth declare it, that they may have glad tidings of great joy; yea, and he doth sound these glad tidings among all his people, yea, even to them that are scattered abroad upon the face of the earth; wherefore they have come unto us. (Alma 13:22--italics added)
Of course this phrase is also found in Luke 2:10: there were certain shepherds in the field watching their flocks, and the angel of God came and said "Fear not; for, behold, I bring you good tidings of great joy." This is an oriental form. In Greek it has been strained, and in English even more strained. But it's the masdar. When you want to make something extremely emphatic, the masdar is to repeat the verbal noun. For example, in Arabic it's not right to say, "He rejoiced greatly." You have to say, "He rejoiced a great rejoicing or a great gladness." So we have that form there, joy and gladness; or fear and trembling. You always intensify it. That's biblical parallelism. This is the way it is in the Bible. . . . The angel came to Benjamin with the same formula. He is speaking the same language here that he spoke in Israel. More importantly, however, the angel is declaring the Christmas message. The birth of Christ is exactly what he is predicting:
For behold, the time cometh and is not far distant, that with power, the Lord Omnipotent who reigneth who was, and is from all eternity to all eternity, shall come down from heaven among the children of men, and shall dwell in a tabernacle of clay, and shall go forth amongst men . . .
[Hugh W. Nibley, Teachings of the Book of Mormon, Semester 1, pp. 462-463]