Deuteronomy 17:16-17

Further, he shall not acquire many [war] horses for himself, nor make the people return to Egypt in order to acquire horses [to expand his military power], since the LORD said to you, ‘You shall never return that way again.’ He shall not acquire multiple wives for himself, or else his heart will turn away [from God]; nor [for the same reason] shall he acquire great amounts of silver and gold.