Revelation 14:3-4

And they were singing a wonderful new song before the throne, in front of the four living creatures, and in front of the twenty-four elders. No one could learn that song except the 144,000 who had been redeemed and who have not defiled themselves with women, for they are virgins, and they join themselves to the Lamb wherever he goes. They have been purchased from humanity and brought forth as the firstfruits for God and the Lamb.