The Geneva Bible Translation Notes, [1599], at sacred-texts.com
(a) Meaning the Philistines.
(b) Forty and two years old [was] Ahaziah when he began to reign, and he reigned (c) one year in Jerusalem. His mother's name also [was] Athaliah the daughter (d) of Omri.
(b) Read (Ch2 21:20).
(c) That is, after the death of his father.
(d) She was Ahab's daughter, who was the son of Omri.
Wherefore he did evil in the sight of the LORD like the house of Ahab: for they were his (e) counsellors after the death of his father to his destruction.
(e) He shows that it follows that the rulers are as their counsellors are and that there cannot be a good king who allows wicked counsellors.
And the destruction of Ahaziah (f) was of God by coming to Joram: for when he was come, he went out with Jehoram against Jehu the son of Nimshi, whom the LORD had anointed to cut off the house of Ahab.
(f) By this we see that nothing can come to any but by God's providence and as he has appointed, and therefore he causes everything to serve his purposes.
And he sought Ahaziah: and they caught him, (for he was hid in Samaria,) and brought him to Jehu: and when they had slain him, they buried him: Because, said they, he [is] the son of (g) Jehoshaphat, who sought the LORD with all his heart. So the house of Ahaziah had no power to keep still the kingdom.
(g) This was the just plague of God because he joined himself with God's enemies: yet God to declare the worthiness of Jehoshaphat his grandfather moved them to give him the honour of burial.
But when Athaliah the mother of Ahaziah saw that her son was dead, she arose and (h) destroyed all the seed royal of the house of Judah.
(h) So that there would be no one to claim the crown and so she might usurp the government.
And he was with them hid in the (i) house of God six years: and Athaliah reigned over the (k) land.
(i) Meaning, in the chamber where the priests and Levites slept, who kept their courses weekly in the temple.
(k) That is, of Judah.