Kings of Israel and the prohibition of "many wives"

Question

The Torah explicitly states that kings should refrain from having many wives (Devarim 16:17):

וְלֹ֤א יַרְבֶּה־לּוֹ֙ נָשִׁ֔ים וְלֹ֥א יָס֖וּר לְבָב֑וֹ וְכֶ֣סֶף וְזָהָ֔ב לֹ֥א יַרְבֶּה־לּ֖וֹ מְאֹֽד׃
And he shall not have many wives, lest his heart go astray; nor shall he amass silver and gold to excess.

At least according to the Sefer HaChinuch (mitzvah 501) which cites Sanhedrin 21a a king is permitted to marry up to 18 wives. I have picked this source, but there may be other opinions that disagree with the number 18; that may very well affect the outcome of this answer.

As far as I know, King Solomon had many more. In view of the above, how did he find a permission to do so? From some of the links below, it is suggested that to maintain peace this was a 'standard practice' and (I guess) overrides the prohibition of kings having many wives? I don't quite understand this line of reasoning, because there are many mitzvot that one could argue would ensure peace if only we transgress them somehow.

There may be other kings who also had more wives; I would be interested to hear a line of reasoning pertaining to those kings as well.

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Note: from what I can see, other questions (How did King Solomon and King David keep up his duties to his wives, Questions about Polygamy in Jewish Law and Culture) generally deal with polygamy, but this question is specifically related to the prohibition against kings having many wives.

Answer 1

As @DoubleAA points out, this is something that Shlomo may have not followed.

The Gemara in Sanhedrin 21b says expressly:

ואמר ר' יצחק מפני מה לא נתגלו טעמי תורה שהרי שתי מקראות נתגלו טעמן נכשל בהן גדול העולם כתיב (דברים יז, יז) לא ירבה לו נשים אמר שלמה אני ארבה ולא אסור וכתיב (מלכים א יא, ד) ויהי לעת זקנת שלמה נשיו הטו את לבבו

And Rabbi Yitczḥak said: For what reason were the rationales of Torah commandments not revealed? It was because the rationales of two verses were revealed, and the greatest in the world, King Solomon, stumbled. It is written (with regard to a king): “He shall not add many wives for himself, that his heart should not turn away” (Deuteronomy 17:17). Solomon said: I will add many, but I will not turn away (as he thought that it is permitted to have many wives if one is otherwise meticulous not to stray). And it is written: “For it came to pass, when Solomon was old, that his wives turned away his heart after other gods” (I Kings 11:4).¹

The Yerushalmi Sanhedrin 2:6 says even more clearly:

אָמַר רִבִּי אָחָא. אָמַר שְׁלֹמֹה. שְׁלֹשָׁה דְבָרִים שֶׁסִּחֲקָה עֲלֵיהֶן מִידַּת הַדִּין חִילַּלְתִּים. לֹא יַרְבֶּה לּוֹ נָשִׁים. וְכָתוּב וְהַמֶּ֣לֶךְ שְׁלֹמֹ֗ה אָהַ֞ב נָשִׁ֧ים נָכְרִיּ֛וֹת. רִבִּי שִׁמְעוֹן בֶּן יוֹחַי אָמַר. אָהַב מַמָּשׁ לִזְנוּת. חֲנַנְיָה בֶּן אֲחִי רִבִּי יְהוֹשֻׁעַ אוֹמֵר. עַל שֵׁם לֹא תִּתְחַתֵּן בָּם. רִבִּי יוֹסֵי אוֹמֵר. לְמוֹשְׁכָן לְדִבְרֵי תוֹרָה וּלְקָֽרְבָן תַּחַת כַּנְפֵי הַשְּׁכִינָה. רִבִּי לִיעֶזֶר אוֹמֵר. עַל שֵׁם גַּם־אוֹת֣וֹ הֶחֱטִ֔יאוּ הַנָּשִׁ֖ים הַנָּכְרִיּֽוֹת׃ אַשְׁכַּח תֵּימַר. רִבִּי שִׁמְעוֹן בֶּן יוֹחַי וַחֲנַנְיָה וְרִבִּי לִיעֶזֶר חָדָא. וְרִבִּי יוֹסֵי פְלִיג עַל תַּלְתֵּיהוֹן

Rebbi Aḥa said: Solomon said, three things I desecrated where I got the better of the law. He shall not add wives, and it is written: King Solomon loved foreign women. Rebbi Simeon ben Ioḥai said, he really made love to them immorally. Ḥananiah, Rebbi Joshua’s nephew, says, because you shall not intermarry with them. Rebbi Yose said, to draw them to the words of the Torah and bring them under the Wings of the Divine Presence. Rebbi Eliezer said, because also the foreign wives made him sin. It turns out that one may say that Rebbi Simeon ben Ioḥai, Ḥananiah, and Rebbi Eliezer mean the same. Rebbi Yose disagrees with all three of them. (Sefaria translation)

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¹ Also note the Midrash in Shir HaShirim Rabbah 1:10:

One of the names of Shlomo was Lemuel (למואל) a contraction of the words נם לא-ל - 'for he spoke to G-d' - the idea being that despite taking many wives, horses and money, he did not feel that he would go astray and sin:

לְמוּאֵל, שֶׁנָּם לָאֵל בְּכָל לִבּוֹ, אָמַר יָכוֹל אֲנִי לְהַרְבּוֹת וְלֹא לַחֲטוֹא

Lemuel - since he spoke to G-d with all his heart. He said, "I am able to have many (i.e. wives, horses & money) and won't sin.