Hisgalus 14:3

Orthodox Jewish Bible

³ And they sing, as it were, a Shir Chadash (New Song) before the Kes (Throne) and before the Arbah Chayyot (four living beings) and before the Zekenim (Elders, Ex 12:21), and no one was being able to learn the Shir (Song) except the 144,000, the ones for whom the Geulah price had been paid for their redemption [Lv 5:5-6; Ex 13:13], the ones having been redeemed (purchased) from ha’aretz (the earth).