Who are the white-robed people standing before the throne in the verse 9 vision?
The white-robed multitude are converted Gentiles from every tongue, tribe, and nation, won through the ministry of the 144,000 during the tribulation. They stand before the throne and the Lamb because they came out of the great tribulation, washed their robes white in the blood of the Lamb, and many were martyred.
Les explains that the 144,000 Jews will minister to all the Gentile nations, not Israel per se, and many will come to salvation through their ministry. In the verse 9 vision, those converted people stand before the throne and before the Lamb, clothed with white robes and palms in their hands, crying that salvation belongs to God and the Lamb. He also notes they will be martyred almost as fast as they are converted throughout the tribulation. Then in Revelation 7:13-14, the elder identifies them as those who came out of the great tribulation and washed their robes and made them white in the blood of the Lamb.