New Defender's Study Bible Notes
6:1 the Lord. Adonai is the divine name of God as seen in Isaiah’s vision (Isaiah 6:8,11). However, the Seraphim call Him Jehovah Sabaoth meaning “LORD of hosts” (Isaiah 6:3).
6:2 seraphims. This is the only reference in the Bible to these angelic beings, perhaps similar in rank to the cherubim, yet different in function. The name, seraphim, literally means “burners.” It is barely possible that these are the same as the cherubim.
6:3 Holy, holy, holy. The threefold ascription of holiness to the One on the throne suggests His tri-unity.