‘ETERNITY OF BEING is a natural attribute of the Godhead: Ge. 21:33; De. 33:27; Ps. 9:7; 41:13; 90:2; 93:2; 103:17; Is. 26:4; 40:28; 44:6; 48:12; Ro. 1:20; 16:26; He. 9:14; Re. 4:8.
From our natural observations we conclude that we ourselves had a beginning, and as far as this earthly life is concerned have a termination. There must be a cause that is not subject to our temporary limitations. We were caused or brought into existence by our parents, they by theirs, and so back through the ages. A point is reached in the long chain of cause and effect where a First Cause is arrived at. This First Cause must have self-sustaining (or un-caused) life. Hence, the idea of eternal existence springs up in our minds. The idea of an eternal First Cause also arises in our minds from our observation of the constancy of the many things and operations about us. God being un- caused must therefore be independent of our limitations. The Bible overwhelmingly establishes the idea that time or duration is an element in God’s existence, and equally asserts that the Being of God is without beginning or ending. God, therefore, inhabits eternity, and beyond this we cannot go in our thinking.’
Source: Gordon Olson, The Truth Shall Make You Free, The Truth About The Nature and Character of God, p 22-23 (Illinois, Bible Research Fellowship Inc., 1980)