Exodus 28:39

Now the embroideries of the vestures shall be of cotton and thou shalt make a tiara of cotton, and thou shalt make a girdle, the work their nakedness. These shall reach from the loins to the thighs, and Aaron and his sons shall wear them when they come into the tabernacle of the testimony or when they come near to minister at the altar of the sanctuary, that they may not bring sin upon themselves and die. This shall be a perpetual statute for him and his seed after him.