Mishneh Torah — Negative Mitzvot מצוות לא תעשה, Chapter 101
The full Hebrew text of Mishneh Torah, Negative Mitzvot, Chapter 101, with English translation by Maimonides (Rambam).
שלא לשחוט אותו ואת בנו, שנאמר "אותו ואת בנו, לא תשחטו ביום אחד" (ויקרא כב,כח).
Not to slaughter an animal and its offspring on the same day, as [Leviticus 22:28] states: "Do not slaughter it and its offspring on the same day."