2 Kings 15:30 - Matthew Poole's English Annotations on the Holy Bible

Smote him, and slew him; which he did more easily effect, because the people were enraged against Pekah, as the man who by his murder of king Pekahiah the son of Menahem, whom the Assyrian monarch set up and favoured, and by his unnecessary war with Ahaz, had brought the Assyrian upon them, and caused the loss of one half of that kingdom. In the twentieth year of Jotham the son of Uzziah. Quest. How could this be, when Jotham reigned only sixteen years, below, 2 Kings 15:33 ? Answ. The meaning is, that he began his reign in the twentieth year after the beginning of Jotham's reign; or, which is the same thing, in the fourth year of Ahaz, son of Jotham, as appears from 2 Kings 16:2. But the sacred writer, having not yet made mention of Ahaz, thought it more proper to number Hoshea's years by Jotham, of whom he had spoken, than by Ahaz. Besides, as Jotham did reign divers years in his father's life, so might Ahaz in Jotham's life, and Jotham might for divers reasons (which it is needless here to inquire) resign up the administration of the kingdom wholly into Ahaz's hands some years before his death, and therefore might be said to reign but sixteen years, though he lived longer.