Numbers 5:14-15

14But the man may think that it happened. He will be angry. But she may not have made herself unclean in that way.

15The man must take his wife to the priest. He must bring one kilogram of barley flour with him. This is a grain offering to discover if his wife really did do those things. So he must not put oil or incense on the grain offering. That is an offering because the man does not trust his wife.