Ezekiel 44:17-18

17When they come through the gates into the inside yard, they must wear linen clothes. The clothes that they wear while they serve me must not have any wool in them. They must wear linen clothes when they work at the gates of the inside yard or in the temple.

18They must wear linen cloths around their heads. The trousers that they wear next to their skin must also be made of linen. They must not tie anything around their body that makes them sweat.