The pasuk says in Devorim 22:10 “Do not plow together with an ox and a donkey”. This is one of several forms of the prohibition of Kilayim – mixing of species. There is a form of this prohibition relating to garments (Kilaei Begadim or Shatnez). Finally, this pasuk prohibits the yoking together of different species of animals.
The Daas Zekeinim provides an interesting reason for this Issur. A donkey does not chew its cud. An ox, on the other hand, does chew its cud. The donkey and the ox would be walking along, yoked together, and the donkey would see the ox chewing and think that it was eating something. The donkey would become upset: “I missed my feeding. When did it happen?” He would become jealous of the ox, because he would think the ox was fed and he was not.
In fact, of course, they both had the same feeding. But the ox chews its cud so it appears to be continuously eating, thus giving the donkey the misimpression that he has been cheated. According to the Daas Zekeinim, the Torah is trying to avoid this psychological pain that the donkey would experience. R’ Chaim Shmuelevitz Zt”l explains, we see from here that the Torah was worried about the feelings of an animal… all the more so for a human being!
We should all be very careful not to boast about our accomplishments or possessions if others might feel envious. Do not praise someone in the presence of a person who might feel envious of that person.
