Ahaz was twenty years old when he became king, and he reigned in Jerusalem sixteen years. And unlike David his father, he did not do what was right in the eyes of the LORD his God.
We have here a general character of the reign of Ahaz. Few and evil were his days - few, for he died at thirty-six - evil, for we are here told, 1. That he did not that which was right like David (Kg2 16:2), that is, he had none of that concern and affection for the instituted service and worship of God for which David was celebrated.
Commenting on 2 Kings 16:1-4
But he walked in the way of the kings of Israel..... Worshipping the calves as they did; which, as it was contrary to the religious sentiments in which he was educated, so against his political interest, which was the only, or at least the principal thing, which swayed with the kings of Israel to continue that idolatry: yea, and made his son to pass through...
Twenty years old was Ahaz - Here is another considerable difficulty in the chronology. Ahaz was but twenty years old when he began to reign, and he died after he had reigned sixteen years; consequently his whole age amounted only to thirty-six years.