Cross reference
Leviticus 15:6
6 He who sits on anything whereon the man who has the discharge sat shall wash his clothes, and bathe himself in water, and be unclean until the evening.
Isaiah 1:16
16 Wash yourselves, make yourself clean. Put away the evil of your doings from before my eyes; Cease to do evil.
James 4:8
8 Draw near to God, and he will draw near to you. Cleanse your hands, you sinners; and purify your hearts, you double-minded.