What does this Mizmor discuss?
Radak: It is about the length of Galus, in which Malchus Beis David has been Batel for many years.
Malbim: It is about the Galus, and the Bris that Hashem made with Beis David. It was annulled; no descendant of his is ruling over Yisrael. It explains that Hashem's general conduct of the world is based on Chesed and Emunah. Also the Bris with David is based on these two pillars.
Who is Eisan ha'Ezrachi?
Rashi: He is one who five brothers who were singers in the Mikdash. (Presumably, one of them was Heiman ha'Ezrachi, to whom Mizmor 88 is attributed - PF. Refer to 88:1:5:1.)
Rashi (from Bava Basra 15a): It is Avraham, about whom it says "Mi He'ir mi'Mizrach" (Yeshayah 41:2).
Radak: He is [one of the Chachamim] mentioned in "va'Yechkam mi'Eisan ha'Ezrachi
The verse implies that he was the son [and not merely a descendant] of Zerach, and so explain all the Meforshim there. Presumably, he died long before Shlomo, who was 700 years after Zerach descended to Egypt. (PF)
