With this action the angel demonstrates that the Lord God answers the prayers of the saints. Those under the altar (Revelation 6:9–10) had called out to ask God when he would avenge their blood. Those prayers are sweet‑smelling to God (recall the incense) and so pleasing to him—and so he answers. That is the purpose of the angel throwing fire on the earth.
5 Et l'ange prit l'encensoir, le remplit du feu de l'autel, et le jeta sur la terre. Et il y eut des voix, des coups de tonnerre, des éclairs, et un tremblement de terre.