Does the "great multitude which no one could number (Revelation 7:9)" refer to the raptured saints?
Yes, that is correct. Revelation 7:9
says, "After these things I looked, and behold, a great multitude
which no one could number, of all nations, tribes, peoples, and
tongues, standing before the throne and before the Lamb, clothed
with white robes, with palm branches in their hands." From the
phrase, "of all nations, tribes, peoples, and tongues… clothed with
white robes," we can see that with their faith in the gospel of
the water and the Spirit, a countless multitude among the Gentiles
would fight against and overcome the Antichrist, be martyred, and
participate in the first resurrection and the rapture.
Although in these last days the Antichrist runs amok with impunity, we can also recognize that at the same time, there would rise even more people who believe in the gospel of the water and the Spirit given by God. As such, a great multitude would rise among the Gentiles also, a multitude so great that no one could even number, who would be saved from sin by believing in the gospel of the water and the Spirit and embrace their martyrdom with their faith.
Revelation 7:14 says, "So he said to me, 'These are the ones
who come out of the great tribulation, and washed their robes and
made them white in the blood of the Lamb.'" As the Great Tribulation
came upon this earth, these people were saved from sin by believing
in the gospel of the water and the Spirit preached by God's Church
with all their hearts. They therefore were martyred, for they neither
worshipped the Antichrist nor received the mark of the Beast on
their right hand or the forehead, and thereby joined in the saints'
resurrection and rapture. This is why they stand before the throne
and before the Lamb and praise; "Salvation belongs to our God
who sits on the throne, and to the Lamb!"
God, therefore, is not just the God of the Jewish people, but He is also the God of the Gentiles. As such, He will make sure that when the last days of the Great Tribulation come, a countless number of Gentiles from all nations, tribes, peoples, and tongues would believe in the gospel of the water and the Spirit, receive the remission of sin, and stand among the martyrs' file.