The pontiff railed against employers who mistreat and underpay their workers during his general audience.
So-called dirty money is a theme that the pope has frequently spoken out on, denouncing how the wealthy exploit the poor and working class for their own profit, sometimes subjecting workers to slave-like conditions.
Pope Francis told the crowd in St Peter's Square that when he thinks about church benefactors who offer donations that are "fruit of the blood" of exploited workers, he tells them: "Please, take your cheques back and burn them."
He concluded: "The people of God and the church don't need dirty money.
"They need hearts that are open to the mercy of God."
