A New SongBy Rabbi Jack Abramowitz
David says that, even though the Book of Psalms is nearly through, we should all continue to compose and sing new songs of praise to G-d. The Jews should rejoice in He Who made them and selected them as His special nation. They should praise Him with all forms of instruments, both percussion and string.
G-d desires the service of His people and He grants them salvation. The pious will even praise G-d in their sleep, as they slumber soundly without any worries or fears. The praises of G-d are as powerful in their hands as a double-edged sword is in the hand of a warrior. The praises they sing will empower them to avenge themselves on those who have oppressed them; the nations will receive the punishments foretold for them in the Books of the Later Prophets (Rashi refers specifically to Ezekiel). G-d is a source of glory towards His devoted, so they should praise Him!