1,161. Shaatnez with Hides or Leather
176:2 Sheep hides that are made into garments may be sewn with linen thread; we are not concerned about the stray strands of wool even though we are using linen thread. Since the wool hairs are not threads, they are not important and they are nullified.
176:3 According to the Rambam, it is Biblically prohibited to join wool and linen together on either side of a third material, such as attaching wool to one side of a piece of leather and linen to the other side. Other authorities do permit this. According to those authorities, pieces of leather that are sewn together with linen thread may be lined with wool. This is permitted even though the hemp thread used to attach the wool lining might mingle with the linen thread that was used to attach the pieces of leather. The accepted practice is to follow the lenient position but a scrupulous person should follow the more stringent position of the Rambam.