Before God answers their question ("How long . . .?"), they are each given a white robe. Much has been made of the fact that this robe is a stolé, a long, stately, often status-indicating garment, while the overcomer in Sardis receives a white himation, an ordinary outer garment like a cape or cloak (Revelation 3:5). This distinction should not be taken too far, as Christ Himself returns in a himation dipped in blood (Revelation 19:13), not a stolé. The important element is that the robe is white, the color of purity and righteousness, as well as joy, victory, and perfection. The giving of a white robe, formal or common, is a symbol of salvation for these martyred Christians.
Finally, God responds to their question: ". . . it was said to them that they should rest a little while longer, until both the number of their fellow servants and their brethren, who would be killed as they were, was completed." The immediate answer, "a little while longer" (literally, "yet a little time"), is ambiguously short-range. At this point in the prophetic timeline as we have learned it—the Great Tribulation has just commenced—this uncertain period is probably at most three and a half years long.
Yet, because Revelation was written to the church late in the first century—more than nineteen hundred years ago—this comforting and expectant phrase implies a longer duration for Christians through the ages since then. II Peter 3:8 reminds us "that with the Lord one day is as a thousand years, and a thousand years as one day." There is even biblical backing to regard the day of the Lord as the whole period since Christ's first advent nearly two millennia ago! Written around the same time as Revelation, I John 2:18 goes even further: "[W]e know it is the last hour"! Certainly, God marks time differently than we do. Nevertheless, the phraseology assures us that, though it is still future, God's vengeance will fall justly on the guilty, and His saints will be free of suffering and receive their promised reward.
Richard T. Ritenbaugh
The Fifth Seal (Part Two)