5 Next, since God justifies, that is, makes men righteous, by healing them from their iniquities, a prayer follows: “Remember me, O Lord, according to the favour that You bear unto Your people”: that is, that we may be among those with whom You are well pleased; since God is not well pleased with them all. “O visit me with Your salvation.” This is the Saviour Himself, in whom sins are forgiven, and souls healed, that they may be able to keep judgment, and do righteousness; and since they who here speak know such men to be blessed, they pray for this themselves....“Visit us,” then, “with Your salvation,” that is, with Your Christ.
“To see the felicity of Your chosen, and to rejoice in the gladness of Your people”: that is, visit us for this reason with Your salvation, that we may see the felicity of Your chosen, and rejoice in the gladness of Your people. For “felicity” some copies read “sweetness;” as in the former passage, “For He is gracious;” where others read, “for He is sweet.” And it is the same word in the Greek, as is elsewhere read, “The Lord shall show sweetness:” which some have translated “felicity,” others “bounty.”
But what means, “Visit us to see the felicity of Your chosen:” that is, that happiness which You give to Your elect: except that we may not remain blind, as those unto whom it is said, “But now ye say we see: therefore your sin remains.” For the Lord gives sight to the blind, not by their own merits, but in the felicity He gives to His chosen, which is the meaning of “the felicity of Your chosen:” as, the help of my countenance, is not of myself, but is my God. And we speak of our daily bread, as ours, but we add, Give unto us....“That You may be praised with Your inheritance.”
I wonder this verse has been so interpreted in many copies, since the Greek phrase is one and the same in these three verses....But since this seems a doubtful expression, if that sense be true according to which interpreters have preferred, “That You may be praised,” the two preceding verses also must be so understood, because, as I have said, there is one Greek expression in these three verses; so that the whole should be thus understood, “Visit us with Your salvation, that You may see the felicity of Your chosen;” that is, visit us for this purpose, that You may cause us to be there, and may see us there; that “You may rejoice in the gladness of Your people,” that is, that You may be said to rejoice, since they rejoice in You; that “You may be praised with Your inheritance,” that is, may be praised with it, since it may not be praised save for Your sake....
Source: The Enarrations, or Expositions, on the Psalms (New Advent)