Deuteronomy 17:20 NKJV
that his heart may not be lifted above his brethren, that he may not turn aside from the commandment to the right hand or to the left, and that he may prolong his days in his kingdom, he and his children in the midst of Israel.
The instructions for the king included being faithful in reading God's Word and living by it. One reason given in the verse above was so that his heart would not be lifted up above his brothers. God frowns on leadership that requires one thing from its subjects while living above the law himself. As kings we must live humbly and set godly examples for others to follow. The verse says this would prolong his life as well as the lives of his children. As kings we must remain cognizant that our actions affect our lives as well as the lives of others. It is an honor to be a king and we should live in a manner worthy of our calling.