Then I saw a new heaven and a new earth; for the first heaven and the first earth passed away, and there is no longer any sea. And I saw the holy city, new Jerusalem, coming down out of heaven from God, made ready as a bride adorned for her husband. And I heard a loud voice from the throne, saying, “Behold, the tabernacle of God is among men, and He will dwell among them, and they shall be His people, and God Himself will be among them, and He will wipe away every tear from their eyes; and there will no longer be any death; there will no longer be any mourning, or crying, or pain; the first things have passed away.” (Revelation 21:1-4, NASB)
John is telling you to think of a world with no sin, no tears, no betrayal, no disappointment, no failure, no rebellion, and no death, and that is what heaven is going to be like. As you begin to meditate on these beautiful truths, you will continually come back and say to the Lord, "Lord, I cannot imagine being eternally free from sin, because I have never even known a moment of such blessedness." Although we cannot experientially relate to such perfection and blessedness, Scripture reminds us to believe and hope in it, because we are going to one day know a world that contains no sin whatsoever. We are going to know a world where there is no suffering, no sorrow, and no death. The Bible continually asks us to think about our life now lived for God, but with all the forms of pain, evil, conflict, and distress of this life removed.
Although we have already spoken about the horrors of hell, there is perhaps one more thing we need to say. It is a surprising thing to note, because so often we speak of hell as a place where God is not. Let me, however, say something provocative. Hell is eternity in the presence of God without a mediator. Heaven is eternity in the presence of God, with a mediator. Hell is eternity in the presence of God, being fully conscious of the just, holy, righteous, good, kind, and loving Father's disapproval of your rebellion and wickedness. Heaven, on the other hand, is dwelling in the conscious awareness of your holy and righteous Father, but doing so through a mediator who died in your place, the One who absorbed the fullness of the penalty of your sin. Heaven is eternity in the presence of God with the One who totally eradicated sin from your life, the Lord Jesus Christ. Hell is eternity in the presence of God without a mediator. Heaven is eternity in the presence of God with a mediator, the Lord Jesus Christ.
-----Ligon Duncan in Fear Not - Death and the Afterlife from a Christian Perspective