Adam Clarke on Ezekiel 44:17

No wool shall come upon them - The reason is plain; wool is more apt than linen to contract dirt and breed insects; linen breeds none; besides, this is a vegetable, and the other an animal substance. It was an ancient maxim, that whatever was taken from a dead body was impure in matters of religion, and should not be permitted to enter into the temple. The Egyptian priests always wore linen on their bodies, and shoes of matting or rushes on their feet. The Mohammedans never write the Koran upon vellum or skin of any kind, as they would consider that as a defilement.