Exodus 28:40-42
28:40 “For Aaron’s sons you are to make tunics, sashes, and headbands for glory and for beauty.
28:41 “You are to clothe them – your brother Aaron and his sons with him – and anoint them and ordain them and set them apart as holy, so that they may minister as my priests.
28:42 Make for them linen undergarments to cover their naked bodies; they must cover from the waist to the thighs.