Negative commandment · Lo Ta’aseh #364 of 613
For a king not to accumulate many wives
שלא ירבה המלך נשים
The verse · Devarim 17:17
וְלֹא יַרְבֶּה־לּוֹ נָשִׁים וְלֹא יָסוּר לְבָבוֹ וְכֶסֶף וְזָהָב לֹא יַרְבֶּה־לּוֹ מְאֹד
“Neither shall he multiply wives to himself, that his heart turn not away: neither shall he greatly multiply to himself silver and gold.”
The Rambam’s words
For a king not to accumulate many wives, as [Deuteronomy 17:17] states: "And he may not accumulate many wives."
שלא ירבה המלך נשים, שנאמר "לא ירבה לו נשים" (דברים יז,יז).
Who & when
“And it is practiced at the time that we have a king.”
Where in the Mishneh Torah
Hilchot Kings and Wars הלכות מלכים ומלחמות