Question: "What does it mean that God is eternal?"
The word eternal means "everlasting, having no beginning and no end." Psalm 90:2 tells us about God’s eternality: “Before the mountains were born or you brought forth the earth and the world, from everlasting to everlasting you are God.” Since humans measure everything in time, it is very hard for us to conceive of something that had no beginning, but has always been, and will continue forever. However, the Bible does not try to prove God’s existence or His eternality, but simply begins with the statement “In the beginning God…” (Genesis 1:1), indicating that at the beginning of recorded time, God was already in existence. From duration stretching backward without limit to duration stretching forward without limit, from eternal ages to eternal ages, God was and is forever.
When Moses was commissioned by God to go to the Israelites with a message from Him, Moses wondered what he would tell them if they asked him what God’s name was. God’s reply is most revealing: “God said to Moses, ‘I AM WHO I AM. This is what you are to say to the Israelites: I AM has sent me to you'" (Exodus 3:14). This signifies the real being of God, His self-existence, and that He is the Being of beings. It also describes His eternality and immutability, as well as His constancy and faithfulness in fulfilling His promises, because it includes all time, past, present, and future. The sense is, not only I am what I am at present, but I am what I have been, and I am what I shall be, and shall be what I am. God’s own words about His eternality speak to us from the pages of Scripture.
Jesus Christ, God incarnate, also verified His deity and His eternality to the people of His day by declaring to them, “Before Abraham was born, I AM” (John 8:58). It is clear that Jesus was claiming to be God in flesh because the Jews, upon hearing this statement, tried to stone Him to death. To the Jews, declaring oneself to be the eternal God was blasphemy worthy of death (Leviticus 24:16). Jesus was claiming to be eternal, just as His Father is eternal. This was declared again by John regarding the nature of Christ: “In the beginning was the Word, and the Word was with God, and the Word was God” (John 1:1). From before recorded time, Jesus and His Father were one in essence, and sharing equally in the attribute of eternality.
Romans 1:20 tells us that God’s eternal nature and His eternal power are revealed to us through His creation. All men see and understand this aspect of God’s nature by the witness of the various aspects of the created order. The sun and heavenly bodies continue in their orbits century after century. The seasons come and go in their appointed time; the trees produce leaves in spring and drop them in the fall. Year after year these things continue, and no one can stop them or alter God’s plan. All of this attests to God’s eternal power and plan for the earth. One day, He will create a new heaven and new earth and they, like Him, will continue into eternity. We who belong to Christ through faith will continue through eternity as well, sharing the eternality of our God in whose image we are created.