Revelation 5:8

This transfer triggered an outpouring of praise for the Lamb because it signaled that Christ would begin judging. While the four living creatures and 24 elders prostrated themselves in worship, only the elders had harps (lyres) and bowls. This is clear in the Greek text from the gender of hekastos, translated "each one." [Note: See Swete, pp. 79-80.] They used the harps to praise God in song (Psalms 33:2; Psalms 98:5). This is the only place in Scripture where angels praise God with harps.

John explained that the bowls contained the prayers of God’s people that are like the fragrant aroma of burning incense to Him (cf. Psalms 141:2; Luke 1:10). In the Old Testament the offering of incense was a priestly prerogative (Numbers 16:6-7), so these angels were functioning in a priestly capacity. The Jews believed that angels carried human prayers to God (cf. Revelation 8:3). [Note: Fritz Rienecker, A Linguistic Key to the Greek New Testament, p. 825.] The prayers offered are probably all those as yet unanswered petitions that people have prayed asking God to judge unrighteousness including, "Thy kingdom come, thy will be done in earth as it is in heaven" (cf. Revelation 5:10; Revelation 6:10; Revelation 8:3-5; Matthew 6:10; Luke 18:7-8). [Note: Ladd, p. 89.]