At the outset of Isaiah’s prophetic ministry, God appears to him in the Temple. When the prophet confesses that he is a “man of unclean lips” (Isa 6:5), one of the Lord’s winged seraphim touches a burning coal to his lips in order to purge away his sin (6:6-7). In this way, God prepares Isaiah for his upcoming prophetic work. While Isaiah’s visionary inauguration may seem strange or esoteric, Scripture provides a precedent for this event in the prophetic life of Elijah; the combination of the divine touch and burning coals prepares the prophets for the tough job of speaking for God.
Isaiah recounts that during his Temple-vision “one of the seraphim flew to me with a burning coal (רצפה; ritspah) in his hand… and touched (נגע; naga’) my mouth, saying, ‘Behold, this has touched your lips; your guilt is taken away, and your sin is purged away’” (6:6-7). Since “seraphim” (שׂרפים) comes from a Hebrew verb that means “to burn” (שׂרף; saraph), it is fitting that one of these divine beings should touch Isaiah with a burning coal. After this visionary interaction, God sends Isaiah to his people as a divine mouthpiece.
The biblical text actually prepares the reader to expect that God would employ burning coals in a tactile encounter with the prophet. In 1 Kings 19, when Ahab and Jezebel kill the prophets of Israel a fearful Elijah flees into the wilderness (19:3-4). Despairing to the point of wanting to die (19:4), Elijah falls asleep and an angel touches him just as the seraphim had done to Isaiah: “Behold, an angel touched (נגע; naga’) [Elijah] and said to him, ‘Arise and eat’” (19:5). When Elijah wakes, he sees before him burning coals: “And he looked, and behold, at his head was a cake baked on burning coals (רצפים; retsaphim) and a jug of water” (19:6). The angelic touch and food on burning coals provide Elijah with the energy to travel forty days and nights to Horeb (19:8) for another divine encounter that reinforces the prophet’s mission. Both Elijah and Isaiah receive heavenly encouragement by way of burning coals in order to fulfill their respective prophetic calls.