John saw that the great crowd are all dressed in the same attire and all are holding the same emblems: they are clothed with white robes, and have palm branches in their hands. If it were only white robes that were mentioned, then the reference would be to holiness and purity. But the inclusion of palm branches tells us that a prominent emphasis in the vision is that of victory.
Standing with palm branches was a common way for crowds to celebrate an important triumph (they would also wear white robes on such occasions). To get the point, we must recall that throughout history these people have been on the receiving end, with many of them martyred for their faith. Often the church has seemed to be on the verge of destruction by its enemies. But here is the church triumphant, sharing Christ’s victory.
The angel explains to John that each person in the great crowd has washed his or her robes in the blood of Christ. It is a common biblical image to use clothing to depict a person’s behaviour. Also, it is clear that John is referring to Jesus’ death on the cross of Calvary when he took his perfect life and offered it up to God in the place of sinners. He was their substitute as there he paid the penalty of sin by enduring the wrath of God against it. But notice, each person in the crowd took their robes and washed them in the blood of Christ. Each one responded individually to the message of the cross.
John also describes the song of the crowd: they ‘cried with a loud voice, saying, Salvation to our God which sits upon the throne, and unto the Lamb.’ They sing with meaning, because they knew what it was to be unconverted. But Lord in his mercy saved them and brought them to heaven. And they sing with wonder, as they consider the place to where they have been brought. It is a song to God, about his wonderful grace.
So their song is a message to us. It is a reminder that the day is coming when the redeemed shall stand before the throne. It is being sung to us to cause us to prepare to join the song.