Leviticus 5:11-12

11“If you cannot afford to bring two turtledoves or two young pigeons, you may bring two quarts of choice flour for your sin offering. Since it is an offering for sin, you must not moisten it with olive oil or put any frankincense on it.

12Take the flour to the priest, who will scoop out a handful as a representative portion. He will burn it on the altar on top of the special gifts presented to the Lord. It is an offering for sin.