Albert Barnes on Revelation 19:1

And after these things. The things particularly that were exhibited in the previous chapter. Rev 18:1.

I heard a voice of much people in heaven. The voice of the worshippers before the throne.

Saying, Alleluia. The Greek method of writing Hallelujah. This word--αλληλουια--occurs in the New Testament only in this chapter, Rev 18:1,3,4,6. The Hebrew phrase-- ? Hallelujah--occurs often in the Old Testament. It means properly Praise Jehovah, or Praise the Lord. The occasion on which it is introduced here is very appropriate. It is uttered by the inhabitants of heaven, in the immediate presence of God himself, and in view of the final overthrow of the enemies of the church and the triumph of the gospel. In such circumstances it was fit that heaven should render praise, and that a song of thanksgiving should be uttered in which all holy beings could unite.

Salvation. That is, the salvation is to be ascribed to God. Rev 7:10.

And glory, and honour. Barnes on "Re 5:12".

And power. Rev 5:13.

Unto the Lord our God. That is, all that there is of honour, glory, power, in the redemption of the world belongs to God, and should be ascribed to him. This is expressive of the true feelings of piety always; this will constitute the song of heaven.

(a) "great voice" Rev 11:15 (b) "Alleluia" Rev 19:3,4,6 (c) "Salvation" Rev 7:10,12