1 Chronicles 23:28-29

For their office is to assist the sons of Aaron with the service of the house of the LORD, in the courts and in the chambers and in the purifying of all holy things, even the work of the service of the house of God, and with the showbread, and the fine flour for a grain offering, and unleavened wafers, or what is baked in the pan or what is well-mixed, and all measures of volume and size.