What is the meaning of "Acheihem ha'Mishnim"?
'Rashi' 1 , Vilna Gaon: They were gatekeepers, and were changed to be singers
Radak, Malbim: They were second to them; they were gatekeepers (Malbim ? until now, in the Mishkan).
Even though 'Rashi' implies oppositely, on verse 20 he clearly explains like this. (PF)
Why does it say "Zecharyah Ben", but does not name his father?
'Rashi': This was his name. Radak ? my father similarly explain "Almus la'Ben" (Tehilim 9:1). That Psalm refers to defeating Galyus and Pelishtim fleeing. Even though there is a Kamatz under the Lamed in la'Ben, which is in place of the prefix Hei ha'Yedi'ah (to identify), and it is not normally used for a name, here it is used to teach that he was the singer. If there was a Sheva under the Lamed, it would imply that it refers to a son.
Malbim: It means, Zecharyah ben Ya'aziel and Ya'aziel 1 . Verse 20 mentions Zecharyah and Ya'aziel (but does not say "Ben").
Here it says that Zecharyah, Ya'aziel? were gatekeepers. Verse 20 implies that they sang!
'Rashi': While bringing the Aron, there was not such a need for gatekeepers, so all sang, except for Berachyah and Elkanah (verse 23). David established gatekeepers after he set the Aron in a tent, and they were needed when the Mishkan was in Shilo (Radak ? or Nov and Giv'on).
