Quoting Commentary for II Kings 8:25

forty two years old But in II Kings (8:26), Scripture says: “twenty-two years old.” How is this possible? Moreover, according to this, the son was two years his father’s senior, [because Joram ascended the throne at thirty-two and died eight years later, making him forty years old upon his death,] but two years before Joram his father was born, this decree was issued upon the house of David that it would end with the house of Ahab, and so Scripture states (below verse 7): “And from God was Ahaziah’s downfall, etc.” and on the day that Asa took Omri’s daughter for Jehoshaphat his son, this decree was issued. So it was taught in Seder Olam (ch. 17) and in the Tosefta of Sotah (12:3). But throughout Scripture we do not find that Jehoshaphat married Omri’s daughter, but I did find (above 18:1): “and he allied himself in marriage with Ahab,” and perhaps that was his sister that he married, and in the thirty first year of Asa he married her, as it is said in (I Kings 16:23): “And (sic) in the thirty-first year of Asa, etc. Omri reigned.” And when Asa married his daughter to Jehoshaphat his son, Omri gained importance, and they slew Tibni. Figure from the thirty-first year of Asa until Ahaziah reigned, and you will find forty two years. Further, one verse states (II Kings 8:25): “In the twelfth year of Joram the son of Ahab, etc., Ahaziah the son of Joram reigned,” and another verse states (ibid. 9:29): “And in the eleventh year of Joram son of Ahab, Ahaziah became king.” Perforce, his father did not die until the twelfth year of Joram son of Ahab, because it is written (ibid. 8: 16f.): “In the fifth year of Joram the son of Ahab, etc., Joram the son of Jehoshaphat became king, etc., and he reigned eight years.” And that which Scripture states further, “In the eleventh year of Joram,” is because he reigned one year during his father’s lifetime since his father was smitten with severe illnesses, as it is written (above 21:18.): “And after all this, the Lord plagued him, etc.” (22: 1) “And the inhabitants of Jerusalem made Ahaziah, his youngest son, king,” for one year during his father’s lifetime, and that is what is written: “In the eleventh year of Joram.” And where Scripture says: “In the twelfth year of Joram,” it means that after his father died, it was the twelfth year of Joram.

In the eleventh year of Yorom, son of Achov, Achazyoh became king. Above it states, “In the twelfth year.”¹⁸8:25. And you are forced [to say] that Yehorom his father died in the twelfth year of Yorom, because he became king in the fifth year of Yorom and he reigned for eight years. Why then does it say here, “In the eleventh year”? I say that he reigned one year during his father’s lifetime because he was afflicted with severe maladies, as it is stated, “And after all this, Adonoy afflicted him [in his intestines] with incurable illness, and it was at the end of a year … his intestines came out because of his illness, etc.,”¹⁹II Divrei Hayomim 21:18-19. “and the inhabitants of Yerusholayim made king—Achazyohu.”²⁰Ibid. 22:1. Here it states, “Achazyohu was twenty-two years old when he became king,”²¹Above 8:26. but in Divrei Hayomim [it states], “He was forty-two years old when he reigned.”²²II Divrei Hayomim 22:2. Yehorom, his father, lived for forty years, no more, as it is stated, concerning him, “He was thirty-two years old when he became king, and he reigned eight years [in Yerusholayim].”²³Above 8:17. How then is it possible for a son to be two years older than his father? Rather, twenty years before he was born, which is two years before his father was born, this decree was issued. From the day that Asa took Omri’s daughter in marriage for Yehoshophot his son, a decree was issued upon the House of Dovid that it be destroyed with the House of Achov. And similarly it states, “And from God [it was decreed] for the ruination of Achazyohu, that he come to Yorom, etc.”²⁴II Divrei Hayomim 22:7. Thus it is taught in Seder Olam and in the Tosefta of [Maseches] Sotah.²⁵12:3. However, in all of Scripture, we do not find that Yehoshophot married Omri’s daughter. However, I did find in Divrei Hayomim, “And he intermarried with Achov.”²⁶II Divrei Hayomim 18:1. Perhaps this [refers to] his sister whom he married. He married her in the thirty-first year of Asa, as it is stated, “In the thirty-first year of the reign of Asa, [King of Yehudah], Omri reigned [over Yisroel].”²⁷I Melochim 16:23. And we learned in Seder Olam that he reigned over the entire kingdom, for six years before then he reigned over half the people, and when Asa took his [Imri’s] daughter in marriage to [his son] Yehoshophot, Imri gained prestige, and they assassinated Tivni. Proceed and calculate from the thirty-first year of Asa until Achazyohu’s death and you will find them to be forty-two [years].