Parshas Ki Setzei
“You may not plow with an ox and a donkey together!” (Devarim 22:10)
It is a negative commandment that one may not plow with an ox and a donkey together. The same applies to any two species of animal where one is Kosher and the other is not. Not only is plowing forbidden, but also any other form of work. Examples are threshing, pulling a wagon etc. About this it says “You may not plow with an ox and a donkey together!”.
The root of this commandment is that wanton cruelty to animals is biblically forbidden and it is well-known that all species of animals and birds are very worried about dwelling with those of another species, and they especially do not like working together, as we see with our own eyes that all animals and living creatures stay together with their own species. Every man wise of heart will take a lesson from this and learn from here not to appoint two people whose natures are diametrically opposed to do something together. Examples of this are righteous people with wicked people or degraded people with honored people as if the Torah worries about the pain of animals it definitely worries about the pain of people who have a soul which can try to understand their Creator.
Amongst the laws of this commandment are that the biblical prohibition is only when one of the species is Kosher and the other is not, as their natures are very far removed from each other. However, with two species both of whom are either Kosher or non-Kosher, even though they are completely separate species (e.g. an ox with a goat or a horse and a donkey) there is no biblical prohibition. However, it is rabinically prohibited. It applies both to tame and wild animals.
This commandment applies in all places and at all times both to men and to women.