Ellicott's Commentary for English Readers - Leviticus 22:28
(28) 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.” read more
Ellicott's Commentary for English Readers - Leviticus 22:27
(27) When a bullock, or a sheep, or a goat—The three sacrificial quadrupeds. (See Leviticus 22:19 and Leviticus 17:3-6.)Is brought forth.—From this expression it was enacted during the second Temple that the animal fit for a sacrifice had to be born naturally. One brought into the world by artificial aid was disqualified for the altar.It shall be seven days under the dam.—Under seven days the animal is extremely weak, and unfit for human food, and hence must not be offered as the food of God,... read more