Mishneh Torah — Positive Mitzvot מצוות עשה, Chapter 209
The full Hebrew text of Mishneh Torah, Positive Mitzvot, Chapter 209, with English translation by Maimonides (Rambam).
לכבד החכמים, שנאמר: "מפני שיבה תקום" (ויקרא יט, לב).
To honor the Sages, as [Leviticus 19:32] states: "Rise before an elder."