Be glad in the LORD, and rejoice, ye righteous: and shout for joy, all ye that are upright in heart. Be glad - and rejoice - Let every righteous soul rejoice and glory, but let it be in the Lord. Man was made for happiness, but his happiness must be founded on holiness: and holiness, as it comes from God, must be retained by continual union with him. Probably this verse belongs to the next Psalm, and was originally its first verse.
Commentary on the Bible, by Adam Clarke [1831].