And I said unto him, Sir, thou knowest; and I say unto him, My lord (Revised Version). The expression denotes the utmost respect and reverence, which afterwards induce the seer to worship the angel (see Revelation 19:10; Revelation 22:8).
The structure of this part of the vision recalls Ezekiel 37:3, "And he said unto me, Son of man, can these bones live? And I answered, O Lord God, thou knowest" (cf. Zechariah 4:2, Zechariah 4:4, Zechariah 4:5; John 12:21).
And he said to me, These are they which came out of great tribulation; which come out of the great tribulation (Revised Version). The repeated article is especially emphatic. The question arises What is "the great tribulation" referred to?
Probably all the tribulation which has been passed through by the redeemed, all that which pertained to the life though which they have passed. This tribulation is now completed and past, and is therefore referred to as "the great tribulation."
"These are they which have passed through the great tribulation of their life on earth." This is the view taken by Alford. Dusterdieck refers the expression to the last great trial of the saints before the coming of the Lord.
Some point to particular persecutions as the reference intended, and others consider that "the last great trial to be expected under the seventh seal" is meant. And have washed their robes, and made them white in the blood of the Lamb; and they washed, etc.
That is, during their past life, while they were experiencing the great tribulation, they washed their robes (cf. Revelation 3:4, Revelation 3:5, where those who have "not defiled their garments" and those "that overcome" are to be clothed in white).
Those that overcome and are undefiled, therefore, are those who have washed themselves in the blood of the Lamb, through which only their victory is possible or effective. Arethas, Bede, De Lyra, consider that the robes are washed of those who have endured martyrdom, and that they are washed in the blood of the Lamb, because it is the blood of his members.