Charles Ellicott Commentary Revelation 6:11

"And there was given them to each one a white robe; and it was said unto them, that they should rest yet for a little time, until their fellow-servants also and their brethren, who should be killed even as they were, should have fulfilled [their course]." — Revelation 6:11 (ASV)

And white robes were given . . .—The victims, however, are not forgotten. There was given to them (each) a white robe. The white robes, the glistening apparel of the saints , shall be theirs; each shall receive it. They are robes of righteousness (Revelation 19:8); they are robes of honour (Revelation 4:4), for those who wear them are like God, seeing Him as He is, reflecting His image; they are acknowledged to be His, as they have acknowledged Him to be their God. Persecuted on earth, they are honoured in heaven.

There is also a sense in which a white robe is given to them in the eyes of men: those whose names have been cast out as evil have been honoured by a repentant posterity with the robe of tardy praise; after-generations garnish the sepulchres of the righteous whom their fathers slew. The excommunicated in one age are often the canonised of the next, for the dull world learns slowly, and its purest honours are posthumous. But however this may be, for the suffering saints there is the heavenly robe and the heavenly rest.

It was said to them, that they should rest yet for a little season, until their fellow servants also and their brethren, that should be killed (better, who are to be slain) as they were, should be fulfilled (or, shall have fulfilled their course).—They are to “rest.” This does not mean that they are to cease their cry for vengeance, for the saints have never cried for this; rather, they are to rest, as the souls of the faithful do after they are delivered from the burden of the flesh, in joy and felicity.

But this rest still involves waiting for a little while until their fellow servants and fellow sufferers have also completed their work. A work in service and suffering is given to every disciple. Until these have borne their witness and fulfilled their course (Compare to 2 Timothy 4:7–8 and Acts 13:25), the departed must wait for their perfect consummation and bliss, both in body and soul.