Those who are gathered before the throne of God are the elect of God, the saints of God, those for Whom the substitutionary atonement of Jesus Christ has been applied. This is the doctrine, the teaching of definite atonement and is the teaching of Scripture.
But definite atonement should never be thought of as “tiny atonement” (HT Doug Wilson). Actually, in Revelation, we see two aspects of the atonement. The reality of its definiteness is seen in the specific number allotted to each tribe – twelve thousand from each, no more, no less. This is symbolic of its specificity and its definiteness. But the extent of the atonement is seen when John turned and looked.
What did he see? He saw a multitude that no man can number. This was a fulfillment of what had been promised to Abraham. Abraham, look at the stars – count the sand on the seashore. Can you do that? So shall your descendants be.
And this is why this service of worship is an open, public event – even though it is for Christians. What are we saying when we worship in this way? We are declaring that God sent His only Son, not to condemn the world but rather that the world would be saved through Him. Jesus has come. The world has been saved. The world is being saved. Reconciliation is here. Friendship with God is being brought about.
The author of Hebrews says that while we are told that Jesus rules over all the earth at the right hand of the Father subduing all things, we do not yet see this subduing. But we do see Jesus, made a little lower than the angels, suffering on the cross, now high and lifted up, crowned with glory and honor, that He, by the grace of God, might taste death for everyone.