In God we boast all the day long - That is, continually or constantly. It is not a momentary or temporary expression of our feelings, but it is our habitual and constant employment. We have no other ground of reliance, and we express that reliance constantly. The word rendered “boast” here rather more literally means praise: “In God we praise all the day long.” The idea is, that he was their only ground of confidence. They ascribed all their former successes to him; they had no other reliance now.
And praise thy name for ever - We do it now; we shall never cease to do it.
Selah - On the meaning of this word, see the notes at Psalms 3:2.