made no distinction

God did not treat Jewish believers different from Gentile believers.

making their hearts clean by faith

God's forgiving the Gentile believers' sins is spoken as though he literally cleaned their hearts. Here "heart" stands for the person's inner being. AT: "forgiving their sins because they believed in Jesus" (See: rc://en/ta/man/translate/figs-metaphor and rc://en/ta/man/translate/figs-metonymy)