Deuteronomy 17:19 NKJV
And it shall be with him, and he shall read it all the days of his life, that he may learn to fear the LORD his God and be careful to observe all the words of this law and these statutes,
Moses said the king should read the Word of God so he could learn to fear or reverence the Lord and follow the instructions found in the written Word. As royalty, we must reverence the source of our kingship. Remember Jesus made us kings. We did not do it ourselves. So we must honor Him by following the guidelines He gave for kings. It's all in the Book.