'Coals' in the Bible

Now the servants and the officers were standing there, having made a fire of coals, for it was cold. They were warming themselves. Peter was with them, standing and warming himself.

So when they got out on the land, they saw a fire of coals there, and fish laid on it, and bread.

Therefore "If your enemy is hungry, feed him. If he is thirsty, give him a drink; for in doing so, you will heap coals of fire on his head."