Mishneh Torah — Negative Mitzvot מצוות לא תעשה, Chapter 318
The full Hebrew text of Mishneh Torah, Negative Mitzvot, Chapter 318, with English translation by Maimonides (Rambam).
שלא לקלל אב ואם, שנאמר "ומקלל אביו ואימו, מות יומת" (שמות כא,יז).
Not to curse one's father or mother, as [Exodus 21:17] states: "One who curses his father or mother shall surely die."