A cow and her calf were not to be killed on the same day (Leviticus 22:28; Exodus 23:19; Deuteronomy 22:6,7). The reason for this enactment is not given. A state of great poverty is described in the words of Isaiah 7:21-25, where, instead of possessing great resources, a man shall depend for the subsistence of himself and his family on what a single cow and two sheep could yield.
These dictionary topics are from M.G. Easton M.A., D.D., Illustrated Bible Dictionary, Third Edition, published by Thomas Nelson, 1897. Public Domain, copy freely.
Easton, Matthew George. "Entry for 'Cow'". "Easton's Bible Dictionary".