Commentators unanimously highlight the core principle: uncleanness is far more contagious than holiness. Haggai uses a legal illustration to show that just as a defiled person contaminates everything they touch, the people's inner disobedience and sinfulness rendered all their external works—including their sacrifices and labor on the temple—unclean before God. A holy object did not automatically purify other things, but an unclean source corrupted everything.