Isaiah 6:6,7

The ceremony of purification is in many respects unique, and seems to involve several ideas: (1) It shews that contact with the fire of the divine holiness is not necessarily destructive even to man. It is possible to "dwell with devouring fire" (ch. Isaiah 33:14). (2) It signifies the removal from the prophet of all in him which is incompatible with the holiness of Jehovah. Fire is both a symbol of holiness and an agent of purification (Numbers 31:23; Malachi 3:2). "As earthly fire burns away external impurity, so the heavenly fire burns away the defilement of sin, first from the lips, but through them from the whole man" (Dillmann). (3) It is not without significance that the fire is taken "from off the altar." The hot stone (A. V. live coal) was an implement used in common life for transferring heat from the hearth to where it was required. The meaning of the Seraph's act is that the atoning efficacy of the altar is conveyed to the person of Isaiah, to his lips in particular, because there the sin of his nature had seemed to be concentrated.