Here "heart" is a metonym for "thoughts" or "emotions." Here "shuts up his heart of compassion" is a metaphor for no longer showing someone compassion. Alternate translation: "does not show him compassion" or "does not willingly help him" (See: [[rc://en/ta/man/translate/figs-metonymy]] and [[rc://en/ta/man/translate/figs-metaphor]])