Isaiah 6:7

Isa 6:7 And he laid [it] upon my mouth, and said, Lo, this hath touched thy lips; and thine iniquity is taken away, and thy sin purged.

Ver. 7. And he laid it upon my mouth. ] Not to burn him, for all this was visional, but to expiate and purify his lips by the "spirit of judgment and of burning"; Isa 4:4 to fire him up to a holy contention in godliness, and to fit him yet further for his office, as the apostles were for theirs by cloven tongues of fire Act 2:3-4

And said, Lo, this hath touched thy lips. ] To the sign words are used to make a perfect sacrament. And here the cautiousness of the angel is to be noted. He saith not, I have touched, but, lo, this coal hath touched thy lips. So Paul, "Yet not I, but the grace of God in me." 1Co 15:10 So the good and faithful servant, Not I, but "Thy talent hath gained ten talents." Luk 19:16 The seraph was himself a burning creature, as his very name importeth; howbeit it was not the seraph but the retheph or burning coal that did the deed, that God might have all the glory.

Thine iniquity is taken away. ] Sacraments take not away sin, but only testify that iniquity is purged by Christ alone, who hath merited justification and sanctification.