Psalms 118:108

Free offerings of praise and thanks, (St. Augustine) or the works of supererogation, (St. Hilary, Theodoret, &c.) which are not commanded, though acceptable to God, (Worthington) and undertaken for the sake of greater perfection. (Calmet) --- The evangelical counsels of voluntary poverty, &c., are of this nature. Still we acknowledge that we are useless servants, (Luke xvii. 10.) with regard to God. We can give him nothing, which he has not first given us. Our piety will redound to our own advantage. (Haydock) --- The psalmist may allude to his solemn engagement, (ver. 106.; Calmet) which he made with perfect freedom and willingness, though it was not a matter of choice. (Berthier)