{I say} (eir(886b)a). Perfect active indicative of eipon, "I
have said." "To the Seer's mind the whole scene was still fresh
and vivid" (Swete) like kekragen in  Joh 1:15  and eil(8870)hen
in  Re 5:7 , not the so-called "aoristic perfect" which even
Moulton (_Prol_. p. 145) is disposed to admit. {My lord} (Kurie
mou). "An address of reverence to a heavenly being" (Vincent),
not an act of worship on John's part. {Thou knowest} (su
oidas). "At once a confession of ignorance, and an appeal for
information" (Swete), not of full confidence like su oidas in
 Joh 21:15ff . {They which come out of the great tribulation}
(hoi erchomenoi ek t(8873) thlipse(9373) t(8873) megal(8873)). Present middle
participle with the idea of continued repetition. "The martyrs
are still arriving from the scene of the great tribulation"
(Charles). Apparently some great crisis is contemplated ( Mt
13:19ff.  24:21  Mr 13:10 ), though the whole series may be in
mind and so may anticipate final judgment. {And they washed}
(kai eplunan). First aorist active indicative of plun(935c), old
verb, to wash, in N.T. only  Lu 5:2  Re 7:14  22:14 . This change
of construction after hoi erchomenoi from hoi plun(8873)antes to
kai eplunan is common in the Apocalypse, one of Charles's
Hebraisms, like kai epoi(8873)en in  1:6  and kai plan(8369) in
 2:20 . {Made them white} (eleukanan). First aorist active
indicative of leukain(935c), to whiten, old verb from leukos
(verse  13 ), in N.T. only here and  Mr 9:3 . "Milligan remarks
that _robes_ are the expression of character and compares the
word _habit_ used of dress" (Vincent). The language here comes
partly from  Ge 49:11  and partly from  Ex 19:10,14 . For the
cleansing power of Christ's blood see also  Ro 3:25  5:9  Col
1:20: Eph 1:7  1Pe 1:2  Heb 9:14  1Jo 1:7  Re 1:5  5:9  22:14 .
"The aorists look back to the life on earth when the cleansing
was effected" (Swete). See  Php 2:12f.  for both divine and human
aspects of salvation. {In the blood of the Lamb} (en t(9369) haimati
tou arniou). There is power alone in the blood of Christ to
cleanse from sin ( 1Jo 1:7 ), not in the blood of the martyrs
themselves. The result is "white," not "red," as one might
imagine.