“G‑d continued with the laws governing the sabbatical year, the yearly cycle of holidays, and mixing milk and meat.
You must not eat a young animal cooked in its mother’s milk. Exodus 23:19
Cooking a young animal in its mother’s milk is an act of consummate cruelty. The Torah therefore forbids us not only to cook a young animal in its mother’s milk, but to cook any animal in any other animal’s milk, to eat such a mixture, or even to derive any other benefit from it.
We see here what extremes the Torah goes to in forbidding cruelty towards animals. The precautions the Torah takes to distance us from causing suffering to an animal demonstrate how much care we must take to avoid causing suffering to a fellow human being.1 Likutei Sichot, vol. 6, p. 151.