Isaiah 6:6 - Ellicott's Commentary On The Whole Bible

Then flew one of the seraphims. — In presenting the vision to our mind’s eye we have to think of the bright seraph form, glowing as with fire, and with wings like the lightning-flash, leaving his station above the throne, and coming to where the prophet stood in speechless terror. The altar from which he took the “live coal “ — literally, stone, and interpreted by some critics of the stones of which the altar was constructed — is commonly thought of as belonging, like that of Revelation 8:5; Revelation 9:13, to the heavenly Temple which was opened to the prophet’s view. There seems, however, a deeper meaning in the symbolism if we think of the seraph as descending from the height above the throne to the altar of incense, near which Isaiah actually stood. It was from that altar that the glowing charcoal was taken. What had seemed part of the material of a formal worship became quickened with a living power. The symbol became sacramental. So in Psalms 51:7, the prayer of the penitent is “Purge me with hyssop” — i.e., make the symbol a reality. Fire, it need hardly be said, is throughout the Bible the symbol at once of the wrath and the love of God, destroying the evil and purifying the good (Numbers 31:23; Malachi 3:2; Matthew 3:11; 1 Corinthians 3:15; Hebrews 12:29; 1 Peter 1:7). Isaiah passed, as it were, through the purgatory of an instantaneous agony.