What is the affliction of David's seed?
Radak: The kingship over Yisrael will not return to them. You cannot say that it is another affliction, for all the good kings from David's seed had good and serenity.
Malbim: They will be humbled in front of You.
Why does it say "Lema'an Zos"?
Rashi citing Seder Olam: Corresponding to the 36 years that Shlomo was married to Bas Pharaoh (he married her in his fourth year of kingship), it was decreed that David's kingdom be divided for 36 years. The kingship should have returned in the 16th year of Asa's reign, but he messed up. He sent a bribe to Melech Aram, and did not rely on Hashem. "In the 36th year of Asa's kingship, Basha built Ramah" (Divrei ha'Yamim II, 16:1) - this cannot be, for Asa 'buried' Basha (i.e. Basha died) in Asa's 26th year! Rather, his 16th year is called 36, for it was 36 years after the kingship divided. The verse teaches that in that year, he messed up.
Why does it say "Lo Kol ha'Yamim"?
Rashi: [The decree to split David's kingship was] 'not for all the days', rather, 36 years. In the days of Mashi'ach, kingship (over all of Yisrael) will return to him. Radak - it says "va'Asisem l'Etz Echad", and it says "u'Melech Echad Yihyeh l'Chulam", and it says "v'Avdi David Melech Aleihem" (Yechezkel 37:19, 22, 24). This refutes those who say that we wait in vain for Melech ha'Mashi'ach, for he will not come. The Navi says "Lo Kol ha'Yamim"! From when the kingship was split in the days of Rechav'am, it did not return, for all the days there were two kingdoms, until the exile [of the 10 Shevatim], and when they returned from exile in Bavel, not all the Shevatim returned, only those exiled to Bavel, i.e. Yehudah and Binyamin.
Malbim: There will be days when they will not be afflicted in front of Malchei Yisrael. This also hints to a time at the end of days when the entire kingship will return to Beis David.
