Uzziah

“But after Uzziah became powerful, his pride led to his downfall. He was unfaithful to the Lord his God, and entered the temple of the Lord to burn incense on the altar of incense.” 2 Chronicles 26:16
Uzziah was one of the most popular kings in Judah’s history. He was a godly king, he reigned for 52 years and was well-respected by the people. God gave him success in war, in his building projects, and caused him and the whole nation to prosper.
But like all the kings before and after him, this only lasted as long as Uzziah served the Lord whole-heartedly. Uzziah became proud and thought that he could do whatever he liked – he was the king, after all. So he sought to enter the Holy Place of the temple and offer incense on the altar. Yes, he was seeking to worship God, but he was stepping over the line that God had established. Only the priests were allowed to do this. But Uzziah was not satisfied to let the priest offer incense on his behalf – he wanted to be the one doing it. He did not respect what God had established.
As we read further in the account, when Azariah the priest confronted him there in the temple, Uzziah became angry with him. Then the Lord caused leprosy to break out on his forehead, and he had leprosy for the rest of his life. In the parallel account in 2 Kings 15:1-7, we are not given these details, only that he had leprosy.
There is a lesson here for us. God has decreed the ways in which He is to be approached. If we start to come up with other ways outside of these, He will not be pleased. We must approach Him through the cross of Christ.