1)
Who are "Beis ha'Levi"?
1.
Radak: They are those who sing in front of Hashem, verbally and with instruments.
2)
Who are "Yir'ei Hashem"?
1.
Rashi: They are converts.
2.
Radak #1 : They are Chachamim of Yisrael who isolate themselves in Beis Hashem to learn.
3.
Radak #2: They are [those who fear Hashem] in every nation, who come to pray in Beis Hashem.
3)
Why does it mention Beis Yisrael, Beis Aharon, Beis ha'Levi and Yir'ei Hashem?
1.
Malbim: Every person has a greater Brachah according to his level in Kedushah.
