Numbers 5:15

5:15 then the man must bring his wife to the priest, and he must bring the offering required for her, one tenth of an ephah of barley meal; he must not pour olive oil on it or put frankincense on it, because it is a grain offering of suspicion, a grain offering for remembering, for bringing iniquity to remembrance.

Numbers 5:25-26

5:25 The priest will take the grain offering of suspicion from the woman’s hand, wave the grain offering before the Lord, and bring it to the altar. 5:26 Then the priest will take a handful of the grain offering as its memorial portion, burn it on the altar, and afterward make the woman drink the water.