Deuteronomy 17:16-17

Thomson(i) 16 Because he is not to multiply cavalry for himself, he must not even cause his people to go back to Egypt; in order that he may not multiply his cavalry: the Lord indeed hath said, You shall not henceforth return that way any more. 17 Neither shall he multiply wives to himself; that his heart may not turn aside; nor shall he greatly multiply for himself silver and gold.