Praise ye the Lord (comp. Psalms 104:35; Psalms 105:45). O give thanks unto the Lord (so in Psalms 105:1). Even in their greatest afflictions, the Israelites were bound to give God thanks. His mercies always exceeded his punishments.
For he is good (see the comment on Psalms 100:5). For his mercy eudureth forever. According to Chronicles, this phrase was used at the dedication of David's tabernacle (1 Chronicles 16:34, 1 Chronicles 16:41), and again at the dedication of the temple (2 Chronicles 5:13).
It here first occurs in the Psalms.