Leviticus 22:28 - Ellicott's Commentary On The Whole Bible

Not kill it and her young both in one day. — According to the ancient canons, this prohibition to slaughter the dam and its youngling the same day was not only designed to remind the Israelites of the sacred relations which exist between parent and offspring, but was especially intended to keep up feelings of humanity. Hence the ancient Chaldee version begins this injunction with the words, “My people the children of Israel, as our Father is merciful in heaven, so be ye merciful on earth.”