Sir is κύριε [kyrie] which is frequently translated Lord. Elsewhere, the word is translated master (Mtt. Mat. 6:24); Sir (Mtt. Mat. 13:27; John John 5:7), and lord (Mtt. Mat. 10:24; Luke Luke 12:36; Luke 14:21; Luke 16:3; John John 15:15). It is the respectful address of an inferior to his superior in age or station.1
σὺ οἶδας [sy oidas] , emphatic: you, you know.
the ones who come out
ἐρχόμενοι [erchomenoi] , present participle. They are continually coming out probably the result of ongoing persecution resulting in martyrdom, although the text does not explicitly indicate martyrdom. Present middle participle with the idea of continued repetition. The martyrs are still arriving from the scene of the great tribulation. 2 1Cor. 15:51-52).3
the great tribulation
Literally, the tribulation, the great. The tribulation, points to a definite prophetic period, and not simply to tribulation in general in which all saints shared. The great tribulation cannot be the general troubles that affect Gods people in all ages. The insertion of the definite article marks its speciality.4 This is the unique time of intense tribulation which Jesus predicted (Mtt. Mat. 24:21). During this time, multitudes will die; both unbelievers in judgment and believers through martyrdom and harsh conditions (as these, Rev. Rev. 14:13+). And unless those days were shorted, no flesh would be saved; but for the elects sake those days will be shortened (Mtt. Mat. 24:22). This is the hour of trial which shall come upon the whole world, to test those who dwell on the earth (Rev. Rev. 3:10+). This time of trouble will be especially difficult for the Jewish nation (Jer. Jer. 30:7; Dan. Dan. 12:1, Dan. 12:7; Mtt. Mat. 24:16-20). Yet even this Great Tribulation cannot separate the faithful from the love of Christ, for they are overcomers (Rom. Rom. 8:35-39). See Who is the Overcomer? As we have discussed elsewhere, the Church is not appointed to Gods wrath and is exempted from this hour or trial which God brings upon the whole world to test those who dwell on the earth (Rev. Rev. 3:10+). These believers are those who come to faith after the rapture of the Church. It is interesting to note the accuracy which attends predictions made by those who take Scripture at face value. Walter Scott (1796-1861), writing well in advance of the establishment of Israel in 1948, says of this verse: The great tribulation is yet future. It pre-supposes the Jewish nation restored to Palestine in unbelief , to serve Gentile political ends, and brought there by the active intervention of a great maritime power (Isa. Isa. 18:1). [emphasis added]5 Since 1948, Scotts words, which reflect Gods Word, have come to pass. See Trouble Ahead.
washed their robes
See commentary on Revelation 1:5.
made them white
ἐλεύκαναν [eleukanan] , used to describe making blood-red stains due to sin become white (Isa. Isa. 1:18).6 It may picture not only their salvation (washing away their sins), but also the exchange of garments bloodied by their persecution on earth for clean garments from God.
in the blood of the Lamb
The garments of many were no doubt stained with their own blood. Still, it is the blood of the Lamb which is required for salvation. Their blood, while precious to God (Ps. Ps. 116:15) and spilled as a testimony to God, lacks any redemptive power. See commentary on Revelation 1:5 and Revelation 5:9.
3 John MacArthur, Revelation 1-11 : The MacArthur New Testament Commentary (Chicago, IL: Moody Press, 1999), Rev. 7:14.
6 Frederick William Danker and Walter Bauer, A Greek-English Lexicon of the New Testament and Other Early Christian Literature (Chicago, IL: University of Chicago Press, 2000), 472.