Commonsense should tell us that when something clean and something unclean brush against one another, the unclean object is not improved but the clean object is changed for the worse.
2 Corinthians 6:14-15, “Do not be unequally yoked together with unbelievers. For what fellowship has righteousness with lawlessness? And what communion has light with darkness? And what accord has Christ with Belial? Or what part has a believer with an unbeliever?”