Exodus 28:37-43

28:37 You are to attach to it a blue cord so that it will be on the turban; it is to be on the front of the turban, 28:38 It will be on Aaron’s forehead, and Aaron will bear the iniquity of the holy things, which the Israelites are to sanctify by all their holy gifts; it will always be on his forehead, for their acceptance before the Lord. 28:39 You are to weave the tunic of fine linen and make the turban of fine linen, and make the sash the work of an embroiderer.

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. 28:43 These must be on Aaron and his sons when they enter to the tent of meeting, or when they approach the altar to minister in the Holy Place, so that they bear no iniquity and die. It is to be a perpetual ordinance for him and for his descendants after him.