Cyril of Alexandria — on Isa 6:6 (COMMENTARY ON ISAIAH 1:4)

“Let our lips be touched by the divine coal, which burns away out sins and consumes the filth of our transgressions. Moreover, it makes us zealous by the Spirit. By saying "taken from the altar with tongs," Isaiah means that we receive faith in and knowledge of Christ from the teachings or announcements in the law and the prophets, in which the word of the holy apostles confirms the truth. By quoting from the law and the prophets, the apostles convince their hearers and "touch their lips with the burning coal" in order to lead them to confess faith in Christ.”