How can it be that he was 42 when he became king? His father Yehoram lived only 40 years (32 before he became king, and eight years of kingship ? 21:20)! Also, Melachim II, 8:26 says that he was 22 when he became king!
'Rashi', Rashi (Melachim II, 9:29) and Radak, all citing Seder Olam 17: Two years before Yehoram was born, when Asa married off his son Yehoshafat to Amri's daughter 1 , it was decreed that Malchus Beis David perish with Beis Achav. Verse 7 says that Hashem arranged that Achazyahu fall with Yehoram 2 . The 42 years are counted from the time of the decree 3 . Yehoshafat married her in the 31st year of Asa's reign, for it says "Amri became king in the 31st year of Asa" (Melachim I, 16:23). He became king six 4 years before this over half of Yisrael. In year 31, he reigned over all of Yisrael. He married his daughter to Asa's son and was elevated, and they killed Tivni (who was competing with Amri to become king, from when Zimri died). From Asa's 31st 5 year until Achazyahu became king 6 of Yehudah, was 42 years. Radak ? there were nine of Asa, 25 of Yehoshafat, and eight of Yehoram 7 .
Radak: Yehoram lived more than 40 years. The verse counts only eight years that he ruled strongly, but not from when he fell to the Aravim and also fell sick (21:16-18). He lived another 20 years without Chemdah 8 . When he fell sick, they made his son Achazyahu king at the age of 22, like it says in Melachim. "He ruled one year in Yerushalayim" after his father died. He was 42 when his father died 9 , and they declared him king again; our verse refers to this.
Malbim: When Yehoram ben Yehoshafat fell ill, his son Achazyahu became king, in the 11th year of Yehoram ben Achav. The next year his father died, and he became king absolutely. This also resolves a contradiction in Melachim 10 (refer to Melachim II, 9:29:1:1). "Ben Arba'im" refers to the end of verse 1 (Yehoram was 40 when Achazyahu first ruled); "u'Shetayim Shanah Achazyahu b'Malcho" means that he ruled for two years (including in his father's lifetime), "and one year he ruled in Yerushalayim" alone. I explained above (Divrei ha'Yamim I, 8:31), like the Rashbam (Bereishis 36:12), that the first 11 word of the latter verse can apply to the previous verse.
Rashi (in Melachim): No verse says so! Perhaps "va'Yischaten l'Achav" (above, 18:1) means that Yehoshafat married Achav's sister.
Radak: Yehu killed both of them), and Asalyah killed all seed of the royal family [except for Yo'ash; his mother hid him from Asalyah ? PF].
Malbim: I.e. it was decreed that Amri's kingship would last only 42 years, and all remembrance of him and his seed would be wiped out. Achazyahu was his grandson (via Amri's daughter). Therefore he was killed with Beis Achav, to fulfill "v'Hichrati l'Veis Achav Mashtin b'Kir" (Melachim I, 21:21).
Texts of Radak that say '42 years before' are mistaken. Asa ruled for a total of 42 years, and Achav became king in his 38th year, when Amri died 12 (or six) years later (Melachim I, 16:23, 28-29)! (PF)
Rashi in Melachim and Radak. Presumably, also 'Rashi' should say so; 33 is a printing mistake.
'Rashi'. Why do Rashi in Melachim and Radak say 'until he died'? The verse counts 42 until he became king, and so does Radak's calculation; it omits the year that he reigned! He must say that some years in the calculation were partial years, so there are 42 including the year that he reigned. (PF)
Radak: All of this is far from the simple meaning. What I explained is correct (refer to 8:26:1:2).
Metzudas David: I.e. without satisfaction of fulfilling his desire.
Malbim (Melachim II, 8:26): This is difficult. Achazyahu died together with Yehoram ben Achav, who ruled only 12 years. How can it be that there were 20 years in the middle! (Yehoshafat went with Achav to fight in Ramos Gil'ad when Achav died. If there was no gap in Malchus Yisrael, Yehoram ben Achav died 13 years later, after the reigns of his brother Achazyahu (one year) and himself (12 years). There are not 20 years for Achazyahu to reign between Yehoshafat's death and Yehoram ben Achav's death! Perhaps Radak explains that there was a gap of years that are not attributed to Achav's son Achazyahu or Yehoram, until he was firmly established to be king. - PF)
Also 'Rashi' here and in Melachim resolve the contradiction like Malbim.
Surely, 'last' in our text is a printing mistake. However, Malbim above and the Rashbam said that the word can apply to both verses. Here Malbim explains that "Ben Arba'im" applies only to the previous verse, i.e. Achazyahu was only 22 when he became king! If so, (a) Ben Arba'im should have been written in the previous verse; (b) It should say 'u'Shtei' (and not "u'Shetayim", since it is not connected to Arba'im). The Ta'am of Arba'im (Pashta) implies that it is not connected to the following word! (PF)
Here it says that Asalyah was Bas Amri. Above (21:6), it says that Yehoram married Bas Achav!
Radak: Here she is attributed to her grandfather. We learn from ? "va'Tavonah El Re'u'el Avihen" (Shemos 2:18); he was their grandfather.
