Revelation 7: 9-12

⁹ After this I looked, and there was a great multitude that no one could count, from every nation, from all tribes and peoples and languages, standing before the throne and before the Lamb, robed in white, with palm branches in their hands. ¹⁰ They cried out in a loud voice, saying,

“Salvation belongs to our God who is seated on the throne, and to the Lamb!”

¹¹ And all the angels stood around the throne and around the elders and the four living creatures, and they fell on their faces before the throne and worshiped God, ¹² singing,

“Amen! Blessing and glory and wisdom
and thanksgiving and honor
and power and might
be to our God forever and ever! Amen.”

 

Revelation 7:13-17

 

¹³ Then one of the elders addressed me, saying, “Who are these, robed in white, and where have they come from?” ¹⁴ I said to him, “Sir, you are the one that knows.” Then he said to me, “These are they who have come out of the great ordeal; they have washed their robes and made them white in the blood of the Lamb.

¹⁵ For this reason they are before the throne of God,
    and worship him day and night within his temple,
    and the one who is seated on the throne will shelter them.
¹⁶ They will hunger no more, and thirst no more;
    the sun will not strike them,
    nor any scorching heat;
¹⁷ for the Lamb at the center of the throne will be their shepherd,
    and he will guide them to springs of the water of life,
and God will wipe away every tear from their eyes.”

 

Revelation 14:1

 14 Then I looked, and there was the Lamb, standing on Mount Zion! And with him were one hundred forty-four thousand who had his name and his Father’s name written on their foreheads.

The number 144,000 is also mentioned in Revelation 7:4 as the number sealed from the tribes of Israel. There seem to be many interpretations of this number; one of them is that it is a symbolic number that represents the totality of the number twelve squared, according to wikipedia.

Revelation 14:2-3

² And I heard a voice from heaven like the sound of many waters and like the sound of loud thunder; the voice I heard was like the sound of harpists playing on their harps, ³ and they sing a new song before the throne and before the four living creatures and before the elders. No one could learn that song except the one hundred forty-four thousand who have been redeemed from the earth.

I think these are beautiful verses. I'm especially intrigued by the beginning of verse three where John says "they sing a new song"; the thought of there being a brand new thing that has not been heard ever before, a completely new creation, as an introduction to a better time, is such a hopeful thought.

The writer at bibleref.com proposes some theories about who these choristers may be, (as not much information is given), and says, "Whoever they are, it is clear they are joyfully welcoming the end of the tribulation and the commencement of Jesus' reign on earth."