‘And he came and took the scroll out of the right hand of him who sat on the throne. And when he had taken the scroll, the four living creatures and the twenty four elders fell down before the Lamb, each having a harp and golden bowls full of incense, which are the prayers of the saints, and they sing a new song, saying “You are worthy to take the scroll and to break its seals, for you were slain and purchased for God with your blood those of every tribe and tongue and people and nation, and you made them a kingdom and priests to our God, and they are reigning (or shall reign) on the earth.'
The release of the scroll by the One on the throne demonstrated the authority and rightness of the Lion of Judah and Lamb of God for the task in hand. The Lamb is recognised as having the right and authority to open the scroll, for it is released into His care. Thus the One worthy to open the scroll had to be extremely powerful, and yet have been offered as a sacrifice on behalf of the world which the scroll will affect.
And at this the living creatures and the elders fall down and worship Him, and the elders, the representatives of the church on earth, break into singing holding each in their hands a harp and golden bowls full of incense which are the prayers of God's people. Here we see their priestly function. They are represented as presenting men's worship before God.
The idea of prayers as incense is taken from the words of the psalmist, ‘Let my prayer be set forth as incense before you, the lifting up of my hands as the evening sacrifice' (Psalms 141:2). The golden bowls were those used in the Holy place and the Holy of Holies (e.g. Exodus 25:29; 1 Kings 7:50 contrast v. 45) for the use of the priests. It is clearly the elders' responsibility to gather the prayers of God's people and pass them on to Him (compare Daniel 10:12-13). But there is no suggestion that we should pray to them, and John is later admonished for doing such a thing. The harp was associated with joy, thanksgiving and worship (1 Chronicles 25:1; 1 Chronicles 25:6; Psalms 71:22; Psalms 92:3; Psalms 149:3). The description ‘of every tribe and tongue and people and nation' is an amplification of a phrase in Daniel 3:29.
‘They sing a new song'. Compare Isaiah 42:9-10 where singing a new song occurs because something new is about to happen. The presence and actions of the Lamb produce a different song from the elders than that of Revelation 4:11. It is a new song, the song of redemption. The one thing that has fitted the Lamb for His task is that He has bought for God, through the offering of Himself, people from every nation under Heaven. He has further made them a kingdom, and priests to God (i.e. a kingdom of priests: see on Revelation 1:5-6). They are His kingdom, and His priestly kingdom, given the task of making offerings of praise and thanksgiving (Hebrews 13:15; compare Psalms 107:22; Psalms 116:17) and of presenting God's truth to all.
‘And they are reigning on the earth'. The manuscripts, which are somewhat lacking in Revelation, tend to favour the present tense, but some have the future tense. The present tense, which is most probable, and ties in with the fact that they are enjoying the present position as a kingdom of priests, (note that in 1 Peter 2:9 we are a royal priesthood), stresses that through Christ His people are already reigning, as described in Ephesians 1:20-21 with Revelation 2:6. Compare Romans 5:17; Colossians 3:1. They share with Christ His present reign.
If we prefer the future tense it really says the same. It says that because they are a kingdom of priests they will reign on earth in the forthcoming days. It is a statement of confident assurance in the wellbeing of God's people. They will reign on earth, as one day they will be resurrected and reign with Christ over the universe (2 Timothy 2:12: Revelation 22:5).