1 In the third month after the Israelites went out from the land of Egypt, on the very day, they came to the desert of Sinai. 2 After they journeyed from Rephidim, they came to the desert of Sinai, and they camped in the desert; Israel camped there in front of the mountain. 3 Moses went up to God, and the Lord called to him from the mountain, “Thus you will tell the house of Jacob, and declare to the people of Israel: 4 ‘You yourselves have seen what I did to Egypt and how I lifted you on eagles’ wings and brought you to myself. 5 And now, if you will diligently listen to me and keep my covenant, then you will be my special possession out of all the nations, for all the earth is mine, 6 and you will be to me a kingdom of priests and a holy nation.’ These are the words that you will speak to the Israelites.”
8 and when he had taken the scroll, the four living creatures and the twenty-four elders threw themselves to the ground before the Lamb. Each of them had a harp and golden bowls full of incense (which are the prayers of the saints). 9 They were singing a new song: “You are worthy to take the scroll and to open its seals because you were killed, and at the cost of your own blood you have purchased for God persons from every tribe, language, people, and nation. 10 You have appointed them as a kingdom and priests to serve our God, and they will reign on the earth.” 11 Then I looked and heard the voice of many angels in a circle around the throne, as well as the living creatures and the elders. Their number was ten thousand times ten thousand—thousands times thousands— 12 all of whom were singing in a loud voice: “Worthy is the lamb who was killed to receive power and wealth and wisdom and might and honor and glory and praise!”
Notes and References
"... In Revelation 5:9-10, where the list first occurs in Revelation, John is interpreting Exodus 19:5-6, the well-known statement of the Sinai covenant constituting Israel God's chosen people. In Revelation this statement is applied to the church as the eschatological people of God, the people of the new Exodus, who have been redeemed by the blood of Christ, the eschatological Passover Lamb. The reference to Exodus 19:6 ('you shall be for me a priestly kingdom') in Revelation 5:10 ('you have made them a kingdom and priests to our God') is clear. Less often noticed is that 5:9 alludes to Exodus 19:5: 'you shall be my treasured possession out of all the peoples'. Instead of taking 'out of all the peoples' to mean that God has chosen one of the peoples, John has taken it to mean that members have been drawn from all nations to constitute the church: 'by your blood you have purchased for God [people] from every tribe and language and people and nation'. This is a grammatically quite legitimate interpretation of Exodus 19:5, which John must have thought now yielded its full meaning for the first time in the light of the international character of the New Testament people of God ..."
Bauckham, Richard The Climax of Prophecy: Studies on the Book of Revelation (p. 327) T&T Clark, 1993