God is eternal (see Genesis 21:33 & Deuteronomy 33:27) – everlasting, going on for ever, without beginning or end.
Because God is eternal, He talks about other things that are eternal: perhaps more often than anything else, the notion of eternal life which He is able to give to us (see John 3:16, “For God so loved the world that he gave his one and only Son, that whoever believes in him shall not perish but have eternal life”).
Some of the other things mentioned in the Bible that are eternal are:
• Eternal pleasures (“You make known to me the path of life; you will fill me with joy in your presence, with eternal pleasures at your right hand.” Ps 16:11)
• His eternal word (“Your word, Lord, is eternal; it stands firm in the heavens.” Ps 119:89)
• Eternal laws (“all your righteous laws are eternal” Ps 119:160)
• Eternal kingdom (“His kingdom is an eternal kingdom; his dominion endures from generation to generation.” Daniel 4:3)
• Eternal power (“For since the creation of the world God’s invisible qualities—his eternal power and divine nature—have been clearly seen” Rom 1:20)
• Eternal purposes (“according to his eternal purpose that he accomplished in Christ Jesus our Lord” Eph 3:11)
• Eternal salvation (Jesus “became the source of eternal salvation for all who obey him.” Hebrews 5:9)
• Eternal redemption (Jesus “entered the Most Holy Place once for all by his own blood, thus obtaining eternal redemption.” Hebrews 9:12)
• Eternal glory (“For our light and momentary troubles are achieving for us an eternal glory that far outweighs them all.” 2 Cor 4:18)
• Eternal inheritance (“Christ is the mediator of a new covenant, that those who are called may receive the promised eternal inheritance.” Hebrews 9:15)
• An eternal covenant (mentioned in Hebrews 13:20)
• An eternal house (“For we know that if the earthly tent we live in is destroyed, we have a building from God, an eternal house in heaven, not built by human hands.” 2 Cor 5:1)
And some things we would perhaps rather not think about which are eternal:
• Eternal fire (“If your hand or your foot causes you to stumble, cut it off and throw it away. It is better for you to enter life maimed or crippled than to have two hands or two feet and be thrown into eternal fire.” Matthew 18:8)
• Eternal punishment (“Then they will go away to eternal punishment, but the righteous to eternal life.” Matthew 25:46)