Gabriel is the angel who comes on behalf of the Lord to tell him what will happen: what will happen with the temple, and how the rebuilding of the temple will end. Gabriel gets to do the teaching in God’s service, just as an angel did when the Lord Jesus showed his revelation to John (see Revelation 1:1).
22 He made me understand, speaking with me and saying, “O Daniel, I have now come out to give you insight and understanding.