And when those beasts give glory - As often as those living beings ascribe glory to God. They did this continually Revelation 4:8; and, if the above explanation be correct, then the idea is that the ways and acts of God in his providential government are continually of such a nature as to honor him.

And when those beasts (c) give glory and honour and thanks to him that sat on the throne, who liveth for ever and ever,
(c) God is said to have glory, honour, kingdom, and such like given to him, when we godly and reverently set forth that which is properly and only his.

And when these beasts give glory,.... When they give God the glory of all his perfections, covenant, and promises, and of all the gifts and grace bestowed on them, and of the success of their ministry; and in it glorify Father, Son, and Spirit, who bear their respective parts in the business of salvation; and ascribe to each their due glory in election, redemption, and sanctification:
and honour; in the several parts of religious worship performed by them; and not with their lips only, but with their hearts also:
and thanks; for all blessings, temporal and spiritual, bestowed on them, and on the saints: even
to him that sat on the throne; God the Father, Revelation 4:3;
who liveth for ever and ever; he who is the living God, and will always continue so.

All true believers wholly ascribe their redemption and conversion, their present privileges and future hopes, to the eternal and most holy God. Thus rise the for-ever harmonious, thankful songs of the redeemed in heaven. Would we on earth do like them, let our praises be constant, not interrupted; united, not divided; thankful, not cold and formal; humble, not self-confident.

The ground of praise here is God's eternity, and God's power and glory manifested in the creation of all things for His pleasure. Creation is the foundation of all God's other acts of power, wisdom, and love, and therefore forms the first theme of His creatures' thanksgivings. The four living creatures take the lead of the twenty-four elders, both in this anthem, and in that new song which follows on the ground of their redemption (Revelation 5:8-10).
when--that is, whensoever: as often as. A simultaneous giving of glory on the part of the beasts, and on the part of the elders.
give--"shall give" in one oldest manuscript.
for ever and ever--Greek, "unto the ages of the ages."

And when the living creatures shall give glory and honor and thanks to him that sitteth on the throne. Shall utter such praises as are given in Revelation 4:8. Then the twenty-four elders also join in swelling the anthems. It will be noted that these two classes, whatever they signify, are both about the throne, and both engaged in harmonious praise of the Almighty.
Cast their crowns before the throne. There are four elements in this worship: (1) They fall down; (2) they adore; (3) they cast their crowns before the throne, an act of homage which gives Him who sitteth there all the glory of their crowns; (4) they offer ascriptions of praise.
Worthy art thou, etc. The chorus in which they join ascribes all glory to God as his right as the Creator.
Because of thy will they were. Not as in the Common Version. They do not say that God created all things "for his pleasure," but that his will was the efficient cause.

And when the living creatures give glory - the elders fall down - That is, as often as the living creatures give glory, immediately the elders fall down. The expression implies, that they did so at the same instant, and that they both did this frequently. The living creatures do not say directly, "Holy, holy, holy art thou;" but only bend a little, out of deep reverence, and say, "Holy, holy, holy is the Lord." But the elders, when they are fallen down, may say, "Worthy art thou, O Lord our God."