Here a person is inclined to beseech the Lord. First is acknowledged the eternity of the divine being, or substance. As said: "But thou, O Lord, dost reign forever." Then is expressed the duration of the divine royal glory: "thy throne endures to all generations." Thus, Psalm 102(101):12 states: "But thou, O Lord, art enthroned forever; thy name endures to all generations."
[AD 1274] Thomas Aquinas on Lamentations 5:19