Exodus 28:39-43

Weave the tunic out of fine linen. Make the turban out of fine linen. Make a sash decorated with needlework. For Aaron’s sons, you should also make tunics, sashes, and turbans to mark their honor and dignity. Put these garments on your brother Aaron and on his sons with him. Anoint them with oil, ordain them, and make them holy to serve me as priests. You should also make linen undergarments for them to cover their naked skin from their hips to their thighs. Aaron and his sons should wear this clothing when they go into the meeting tent or when they approach the altar to minister as priests in the sanctuary. Otherwise, they will bring guilt on themselves and die. This will be a permanent regulation for him and for his descendants after him.