Seeing the word eternity may conjure up the image of an outstretched horizon receding as far as we can see, or a type of heavenly realm—an Elysian plain with warm sun and cloudless sky. However, eternity is actually a complex idea that relates to how people understand God and their place in the universe.
While eternity is not something one can actually experience, biblical writers use the concept to describe two related issues: First, biblical writers use eternity as a way to describe divine temporality (as in a quality of God, e.g., Gen 21:33; Deut 33:27; Isa 40:28). Second, they also use eternity to describe the timeframe of future existence for people (as in an afterlife, Tob 3:6; John 3:16).
Eternity as Divine Temporality
Concepts of eternity are rooted in how people perceive time, especially as it relates to God’s interaction with time. There are essentially two options: God is temporal, meaning that he exists in time; and God is atemporal, meaning that he exists apart from time. Because of the difficulty of describing eternity in human language, the Bible seems to hint at both of these options. For example, the psalmist depicts God as living an innumerable number of days (Pss 88:29, 90:2; 1 Chr 16:36) and contrasts God’s life with the brevity of a person’s life (Pss 39:5, 90:3–10, 103:15–17, 144:4). Similarly, God seems to exist in time when he does human-like things such as change his intentions (e.g., Exod 32:14) and dwell among people in the incarnation (John 1:14). In contrast, the Bible also depicts God as apart from creation and, therefore, outside of time (Gen 1:1–5; Deut 33:27; Eccl 3:11; Isa 43:13; Rom 1:20). New Testament books such as John afford Jesus a divine temporality as a function of his divinity (John 1:1, 8:58; and looking back to the Old Testament, see Prov 8:22–31; Isa 9:6; Mic 5:2).
Eternity as Future Existence
These concepts of eternity also affect the way in which people describe their future existence. Because God is eternal, his covenant with his people will also be eternal (Gen 9:16, 17:7; Lev 16:34; 2 Sam 23:5; Sir 44:18, 45:7; Bar 2:35; Heb 13:20). Since the final resting place for those possessing this covenant with God is with God (Dan 12:2; 2 Macc 7:9; 2 Cor 5:1; Rev 21), then it is also, by extension, eternal as God is eternal (Ps 49:9; Eccl 12:5; Isa 45:17). For the New Testament, the culmination of this covenant coming through right belief is eternal life (John 3:16). Thus, when the New Testament speaks of eternity, it also views eternity not just as innumerable days but also as the mode of life with God in the age to come (Mark 10:20; John 4:14). Just as heaven is eternal, so does hell appear to be also (Matt 25:41; 4 Macc 9:9; 2 Thess 1:9; Jude 6–7; Rev 20:10).
The biblical writers could not see or touch eternity; it was only something they could grasp in their mind’s eye. Even when Jesus spoke of heavenly things, the crowds did not grasp his meaning (John 3:12). Yet concepts of eternity allow the reader to contrast the limitations and weakness of their present existence with an outstretched horizon of God’s eternal goodness and love (John 3:16).