Coal

Boyd’s Bible Dictionary:

(glow). The coal of scripture is charcoal, or embers (Prov. 26:2121As coals are to burning coals, and wood to fire; so is a contentious man to kindle strife. (Proverbs 26:21); John 18:18; 21:918And the servants and officers stood there, who had made a fire of coals; for it was cold: and they warmed themselves: and Peter stood with them, and warmed himself. (John 18:18)
9As soon then as they were come to land, they saw a fire of coals there, and fish laid thereon, and bread. (John 21:9)
); heated stones (1 Kings 19:66And he looked, and, behold, there was a cake baken on the coals, and a cruse of water at his head. And he did eat and drink, and laid him down again. (1 Kings 19:6); Isa. 6:66Then flew one of the seraphims unto me, having a live coal in his hand, which he had taken with the tongs from off the altar: (Isaiah 6:6)); metaphorical (2 Sam. 22:9-139There went up a smoke out of his nostrils, and fire out of his mouth devoured: coals were kindled by it. 10He bowed the heavens also, and came down; and darkness was under his feet. 11And he rode upon a cherub, and did fly: and he was seen upon the wings of the wind. 12And he made darkness pavilions round about him, dark waters, and thick clouds of the skies. 13Through the brightness before him were coals of fire kindled. (2 Samuel 22:9‑13); Psa. 18:8,12-138There went up a smoke out of his nostrils, and fire out of his mouth devoured: coals were kindled by it. (Psalm 18:8)
12At the brightness that was before him his thick clouds passed, hail stones and coals of fire. 13The Lord also thundered in the heavens, and the Highest gave his voice; hail stones and coals of fire. (Psalm 18:12‑13)
; Rom. 12:2020Therefore if thine enemy hunger, feed him; if he thirst, give him drink: for in so doing thou shalt heap coals of fire on his head. (Romans 12:20)).

Concise Bible Dictionary: