Commentaire sur Le Deutéronome 17:17

ולא ירבה לו נשים NEITHER SHALL HE MULTIPLY WIVES TO HIMSELF only eighteen, for we find that David had six wives, and it was announced to him (by Nathan the prophet): “[Thus saith the Lord … I gave thy master’s wives into thy bosom] … and if that had been too little, I would add unto thee such and such as these (i.e. twice as many)” (Sanhedrin 21a).

ולא ירבה לו נשים, “and he shall not have too many wives.” Our sages (Sanhedrin 21) put the number of wives a king may have at 18. They base this on the number of wives David had, six of whom were mentioned by name (Samuel II 3,2-5). It says there: “if this is insufficient, I will add for you כהנה וכהנה “twice more the same number,” i.e. another 12 (Samuel II 12,8). The reason the Torah gives for this limitation is: ולא יסור לבבו, “so his heart will not go astray.” It is assumed that a woman may seduce a man to turn from being G’d-fearing, seeing that the original woman Chavah had done exactly that when she seduced Adam into eating from the tree of knowledge (Genesis 3,6).

Except as required to maintain his retinue. Because it is written “for himself.” This implies that he may not accumulate in abundance for himself when he [merely] wants to put it into his treasury. “Except as required to maintain his retinue” means supplying his soldiers and horseman [and] to his servants with food, drink and clothing and all that they need.