Halakhah zu Schemuel II 12:25

That He prohibited the king from having much money specifically for himself. And that is His saying, "and he may not have silver and gold for himself in great abundance" (Deuteronomy 17:17). And the measure of this is that its amount only be according to that which is required for his chariot and his designated servants. But it is permitted that he amass money for the benefit of all of Israel. And God, may He be exalted, has already explained the reason for these three commandments - meaning to say, "he may not have many horses," "he may not have many wives" and "he may not have silver and gold for himself in abundance" - in Scripture. But because their reason and cause was known, a veering away from the law occurred. [This is] that which is already famous in the story of King Shlomo, peace be upon him - in spite of the great level of his knowledge and wisdom, and his being a "friend of God (YedidYah)" (II Samuel 12:25). They, may their memory be blessed, said (Sanhedrin 21b) that there is a hint and message with this to people: That if they knew the reasons for all of the commandments, there would be a veering away. [For] if this one, who was so complete in wisdom and of such great stature, could already imagine and think that this [forbidden] act is not necessarily a cause for that sin; what will be when all of the masses with their weak minds will talk about them and say, "This would not be prohibited or this not commanded except for this. I will be careful about the thing for which this commandment was commanded, and I will not pay attention to it [since it was only meant as a fence]!" But then the law will be destroyed. And hence God, may He be exalted, hid their reasons. But there is none of [the commandments] that does not have a reason, a benefit and a cause. However most of these reasons needed to be hidden; for the intellect of the masses will not grasp and understand them. But they are all like the prophet testified - "The statutes of the Lord are right, rejoicing the heart; the commandment of the Lord is pure, enlightening the eyes" (Psalms 19:9). And I shall ask assistance from God to fulfill that which we are commanded about, and to stay away from that which we are prohibited. (See Parashat Shoftim; Mishneh Torah, Kings and Wars 3.)