Revelation 19:1

The fall of Babylon being fixed, finished, and declared to be irrecoverable in the foregoing chapter, this begins with a holy triumph over her, in pursuance of the order given forth: Rejoice over her, thou heaven, and you holy apostles and prophets, Rev 18:20. They now gladly answer the call; and here you have, 1. The form of their thanksgiving, in that heavenly and most comprehensive word, Alleluia, praise you the Lord: with this they begin, with this they go on, and with this they end (Rev 19:4); their prayers are now turned into praises, their hosannas end in halleluias. 2. The matter of their thanksgiving: they praise him for the truth of his word, and the righteousness of his providential conduct, especially in this great event - the ruin of Babylon, which had been a mother, nurse, and nest of idolatry, lewdness, and cruelty (Rev 19:2), for which signal example of divine justice they ascribe salvation, and glory, and honour, and power, unto our God. 3. The effect of these their praises: when the angels and saints cried Alleluia, her fire burned more fiercely and her smoke ascended for ever and ever, Rev 19:3. The surest way to have our deliverances continued and completed is to give God the glory of what he has done for us.

— Matthew Henry's Concise Commentary (public domain)