Mishnà su Levitico 13:47

Nothing is forbidden on account of kilayim except [a mixture of] wool and linen. No [clothing material] is subject to uncleanness by scale disease except wool or linen. Priests do not wear any materials to serve in the Temple except for wool and linen. Camel’s wool with sheep’s wool, that have been mixed together: if the greater part is camel’s wool, it is permitted [to mix it with linen], but if the greater part is sheep’s wool, it is forbidden; if it is half and half, it is forbidden. The same applies to hemp and linen mixed together.