John himself says that they are the seven spirits of God,
which stands for the fullness of the Holy Spirit (see on Revelation 1:4). That the Spirit is described as torches of fire makes the message clear: even the creatures of heaven need to keep back, and watch out for this God! (Recall Hebrews 12:29.) At the same time, his work through his Spirit is effective.
5 From the throne came flashes of lightning, and rumblings and peals of thunder, and before the throne were burning seven torches of fire, which are the seven spirits of God,