The eternity of God looks both backward and forward, it is both without beginning and without end. The former is affirmed and illustrated Psalms 102:24,26,27, the latter is clearly implied in this verse. Thou hadst a being before the creation of the world, when there was nothing but eternity, but the earth and heavens had a beginning given them by thy almighty power.
Related Commentaries of Psalms 102:25
Psalms 102:25
25 Of old hast thou laid the foundation of the earth: and the heavens are the work of thy hands.