No eye has seen, no ear has heard, no human heart has imagined

This is a triplet referring to all parts of a person to emphasize that no man has ever been aware of the things that God has prepared. (See: rc://en/ta/man/jit/figs-doublet and rc://en/ta/man/jit/figs-metonymy)

what God has prepared for those who love him

The Lord has created in heaven wonderful surprises for those who love him.