1,160. Mules, Shaatnez

175:6  A mule is the offspring of a horse and a donkey, and there are two types: when the father is a horse and the mother a donkey (which we call a hinny in English) and when the mother is a horse and the father a donkey. These are considered separate species, so if one wants to tie two mules together, he must check their distinguishing characteristics: the ears, the tail and the voice. If they are similar, it is clear that their mothers are from the same species and tying them together is permitted. Some authorities are of the opinion that a mule is a mixed animal by itself because it comes from two different species. According to this position, it is forbidden to do work with or to ride on a mule.

176:1 The combination of linen with wool from sheep or goats is prohibited. This forbidden mixture is called shaatnez. This applies: if one sews a wool cloth to a linen cloth, even using silk or hemp thread; if one sews a wool cloth using linen threads or vice versa; if one ties linen thread to wool thread; if one spins these materials together. All these are forbidden as shaatnez. If a person sews a single stitch and ties it, or if he makes two stitches even though he did not tie them, he has made a forbidden shaatnez connection. It is therefore forbidden to connect a wool cloth to a linen cloth even using a pin or a needle without thread.