Numbers 5:15 "He shall pour no oil upon it"

This Negative Mitzvah applies to the meal-offering of a Sotah (see Positive Mitzvah 223).

A "Sotah" is a woman who is suspected of not being faithful to her husband. The Torah requires that she and her husband go to the priest and bring a sacrifice.

Since this is a sacrifice that is connected with a possible sin, it consists of plain barley flour with nothing else added. No oil may be poured over this offering.