Fire
Fire, in the spiritual sense, can mean either love or hatred depending on the context, just as natural fire can be either comforting in keeping you warm, or scary in burning down your house. Our language reflects this, too -- we use concepts like a smoldering hatred or a burning love. So fire signifies a love, either a good love of the neighbor and to the Lord, or, in a bad sense, selfish love of oneself that, if unchecked by conscience, leads to hatred of anyone that opposes it.
Matthew 12:38-40
38
Then certain of the scribes and Pharisees answered, "Teacher, we want to see a sign from you."
39
But he answered them, "An evil and adulterous generation seeks after a sign, but no sign will be given it but the sign of Jonah the prophet.
40
For as Jonah was three days and three nights in the belly of the whale, so will the Son of Man be three days and three nights in the heart of the earth.
