8 And when he had taken the book, the four beasts and four and twenty elders fell down before the Lamb, having every one of them harps, and golden vials full of odours, which are the prayers of saints.
[AD 202] Irenaeus on Revelation 5:8
Since, therefore, the name of the Son belongs to the Father, and since in the omnipotent God the Church makes offerings through Jesus Christ, He says well on both these grounds, "And in every place incense is offered to My name, and a pure sacrifice. "Now John, in the Apocalypse, declares that the "incense "is "the prayers of the saints."

[AD 202] Irenaeus on Revelation 5:8
As John also declares in the Apocalypse: "The incense is the prayers of the saints."
[AD 253] Origen of Alexandria on Revelation 5:8
We regard the spirit of every good person as an altar from which arises an incense that is truly and spiritually sweet-smelling, namely, the prayers ascending from a pure conscience. Therefore it is said by John in the Revelation, “The odors are the prayers of the saints”; and by the psalmist, “Let my prayer come before you as incense.” And the statues and gifts that are fit offerings to God are the work of no common mechanics but are wrought and fashioned in us by the Word of God, to wit, the virtues in which we imitate “the firstborn of all creation,” who has set us an example of justice, of temperance, of courage, of wisdom, of piety, and of the other virtues.

[AD 304] Victorinus of Pettau on Revelation 5:8-9
"Twenty-four elders and four living creatures, having harps and phials, and singing a new song." The proclamation of the Old Testament associated with the New, points out the Christian people singing a new song, that is, bearing their confession publicly. It is a new thing that the Son of God should become man. It is a new thing to ascend into the heavens with a body. It is a new thing to give remission of sins to men. It is a new thing for men to be sealed with the Holy Spirit. It is a new thing to receive the priesthood of sacred observance, and to look for a kingdom of unbounded promise. The harp, and the chord stretched on its wooden frame, signifies the flesh of Christ linked with the wood of the passion. The phial signifies the Confession, and the race of the new Priesthood. But it is the praise of many angels, yea, of all, the salvation of all, and the testimony of the universal creation, bringing to our Lord thanksgiving for the deliverance of men from the destruction of death. The unsealing of the seals, as we have said, is the opening of the Old Testament, and the foretelling of the preachers of things to come in the last times, which, although the prophetic Scripture speaks by single seals, yet by all the seals opened at once, prophecy takes its rank.

[AD 560] Primasius of Hadrumetum on Revelation 5:8
The bowls that are accepted by God are the pious confession in which no one is hidden with a duplicitous heart but is rather sincere with an open affection. They are also the golden vessels that are in the great house, burning with the sweetness of the pleasant odor of Christ. Moreover, the prayers of the saints are the grateful deeds of those who rejoice over the salvation of the world and their intercessions for the wellbeing of the helpless. [The apostle] says, “Christ suffered for us, leaving for us an example that we should walk in his footsteps.” When, therefore, “those who belong to Christ crucify their own flesh with its passions and desires,” it is as though they are playing to Christ on harps, so that what he has done for them, they might do for him, “looking to Jesus, the pioneer and perfecter of our faith.”

[AD 614] Andreas of Caesarea on Revelation 5:8
The harps indicate the harmonious and melodious divine doxology, while the incense indicates the sweet-smelling sacrifice of the faithful that is offered through a most pure life, as the apostle says: “We are the aroma of Christ.” The bowls are symbolic of the thoughts from which the sweet aroma of good works and pure prayer come.

[AD 735] Bede on Revelation 5:8
Just as it is proper for us to seek the Lord shining with the light of good works, so also is it proper for us to seek him abundantly provided with the gift of spiritual prayers. Hence it is good that the women who came to the tomb early in the morning are reported to have been carrying with them the spices that they had prepared. Our spices are our voices in prayer, in which we set forth before the Lord the desires of our hearts, as the apostle John attested in the describing mystically the purest inmost longings of the saints, saying, “They had golden bowls full of incense, which are the prayers of the saints.” What in Greek is called “spice” in Latin is called “incense.” We bear spices to the tomb of the Lord early in the morning when, mindful of the passion and death that he underwent for us, we show to our neighbor outwardly the light of our good actions and are inwardly aflame in our heart with the delight of simple compunction. We must do this at all times, but especially when we go into church in order to pray and when we draw near to the altar in order to partake of the mysteries of the body and blood of the Lord.

[AD 735] Bede on Revelation 5:8
And when He had opened the book, etc. When by His passion the Lord proved that the proclamations of both Testaments were fulfilled in Him, the Church, giving thanks, also offers itself to sufferings, so that, according to the Apostle, it may complete in its flesh what is lacking in Christ’s afflictions (Col. 1). For in the harps where strings are stretched on wood, the bodies ready to die are signified; by the bowls, the hearts open wide in the breadth of charity are signified.

[AD 990] Oecumenius on Revelation 5:8-12
All worshiped the Lord after he had taken the scroll, since they already knew the salvation which he was going to effect for human beings and the punishment he was going to bring on the polluted demons.

The elders’ holding harps indicates the harmony and concord of their confession of God, according to Scripture, “Sing praises to our God, sing praises.”

The incense symbolizes the offering of all the nations, for Malachi, speaking in the person of God, says to disobedient Israel, “I will not accept an offering from your hand, for from the rising of the sun to its setting my name has been glorified among the nations, and in every place incense is offered in my name, and a pure sacrifice,” predicting by these [words] the faith of the nations and their bringing of gifts.

And they sing a new song: for the song sung to God incarnate is new, since it had never been invented before the incarnation.

What was the song? You are worthy, he says, to effect this salvation for human beings, you who were slain for us, and with your blood you took possession of many from among those under heaven.

Very correctly he said from every tribe and tongue and people and nation: for he did not acquire possession of everyone (for many died in unbelief), but only those who were worthy of salvation. The prophet also said something similar, “Arise, O God, judge the earth, because you” will place “your inheritance among all the nations,” where he does not simply say “all the nations.”

And he made them kings and priests to our God, and they shall reign on earth. You can indeed understand this literally, for the kings and presidents of the churches are [God’s] faithful people and servants of Christ. But you can also understand kings to be those who control their passions and are not controlled by them. And you can understand priests to be those who present their own persons “as a living sacrifice, holy and acceptable to God,” as Scripture says.

And he says not only the elders but also the incorporeal powers of the angels were singing a triumphant song to Christ. Daniel also predicted their number as now mentioned. The song of the angels attributes seven different honors to Christ, because by the number seven they indicate that it is fitting for Christ to be crowned with ten thousand praises.