Sir, you know: the title Sir represents the Greek kurios, which may mean “master” or “lord,” or “a respected elder.” Here Sir is the appropriate equivalent in English.

They who have come out of the great tribulation: the verb “to come out (of)” has here the meaning “to survive,” “to live through,” or “pass through … safely.” In 2.22 reference is made to “a great tribulation”; here, however, it is the great tribulation, that is, the time of distress and cruel persecution that will take place before the end of the world (see Matt 24.21). Revised English Bible and New Revised Standard Version translate “the great ordeal,” and Barclay has “the terrible time of trouble.” Or it can be “the time of great (or, terrible) suffering.”

They have washed their robes and made them white in the blood of the Lamb: this figurative language, as elsewhere, is a way of talking about purification from sin by means of the death of Christ (see 1.5b; 22.14; Heb 9.14; 1 John 1.7). For robes see 3.4-5; 6.11; 7.9, 13; 22.14; and for the blood of the Lamb, see 1.5b. There may be a logical inconsistency in the statement that the robes are made white by being washed in blood. It would be very difficult, however, and quite inappropriate to attempt to avoid this inconsistency. As in 1.5, the blood of the Lamb means the sacrificial death of Christ. In certain languages this sentence will be expressed as “They have used the blood of the Lamb to wash their robes and make them white.”

An alternative translation model for this verse is:

• I answered, “I don’t know.”
He said to me, “These are people who have passed through the time of terrible suffering safely (without dying). They have washed their robes in the blood of the Lamb to make them white.

Quoted with permission from Bratcher, Robert G. and Hatton, Howard A. A Handbook on The Revelation to John. (UBS Handbook Series). New York: UBS, 1993. For this and other handbooks for translators see here .