Ahaz was twenty years old when he became king, and he reigned sixteen years in Jerusalem; and he did not do what was right in the sight of the LORD his God, as his father David had done.
2 Kings 16:2
Surrounding context
16:1 In the seventeenth year of Pekah the son of Remaliah, Ahaz the son of Jotham, king of Judah, began to reign.
16:2 Ahaz was twenty years old when he became king, and he reigned sixteen years in Jerusalem; and he did not do what was right in the sight of the LORD his God, as his father David had done.
16:3 But he walked in the way of the kings of Israel; indeed he made his son pass through the fire, according to the abominations of the nations whom the LORD had cast out from before the children of Israel.