Revelation 14:2-3

2I also heard a sound coming out of heaven like the sound of many waters and like the sound of loud thunder. Now the sound I heard was like that made by harpists playing their harps,

3and they were singing a new song before the throne and before the four living creatures and the elders. No one was able to learn the song except the one hundred and forty-four thousand who had been redeemed from the earth.