God's rules for the king

“The king, moreover, must not acquire great numbers of horses for himself or make the people return to Egypt to get more of them, for the Lord has told you, ‘You are not to go back that way again.’ He must not take many wives, or his heart will be led astray. He must not accumulate large amounts of silver and gold.” Deuteronomy 17:16-17
At the time Deuteronomy was written, Israel did not have a king. It was led by God, through Moses. But God knew that in the years to come the nation would demand to have a king over them, so they would be like the other nations (Deut. 17:14, 1 Sam. 8:5). In anticipation of that, He gave them laws concerning the king: he was to be an Israelite, not a foreigner; he was not to amass horses, wives, or silver and gold, and when he took the throne he was to write out for himself a copy of the Law.
God knew that the nation, being comprised of fallen human beings, would someday refuse to be led by Him through prophets and judges. While they would want a king like the other nations, God didn’t want their king to be like those other kings. He wanted the king to live a humble life, relying on Him.
Horses symbolised military strength. God wanted the nation to know that He was the one who would fight their battles and give them victory.
Taking many wives was something that the pagan kings did. Marrying the daughter of a rival king was a way of making a political alliance so the two nations would not fight each other. God didn’t want Israel to make alliances with her enemies as a promise of peace.
Lastly, the king was not to amass silver and gold: things that would either set him above the people, or be used to placate their enemies.
God was teaching Israel that even when they had a king, they were still to trust in Him, and not in their military strength, political alliances, or wealth. There’s a lesson here for us too. What are we trusting in?