1)
Who should praise Hashem?
1.
Radak: Yisrael.
2)
Why should they sing a new Shir?
1.
Radak: Those that are already written will not suffice for them. Make a new Shir for the wonders that He did for you!
2.
Malbim: After mentioning (148:14) the praise of the Chasidim because they are close to Him and He goes among them, it says now that they should sing a new Shir to praise that He is among them and they are His close nation.
3)
What is the meaning of "Tehilaso bi'Khal Chasidim"?
1.
Radak: His praise will be said amidst the congregation of Chasidim, i.e. Yisrael.
2.
Malbim: This (refer to 149:1:2:2) is the praise of the Chasidim who are close to Him.
