Revelation 4:8

And the four living creatures With an allusion to the seraphim represented in Isaiah's vision; had each of them six wings about him Which they used in part to express their reverence and humility, and in part to show readiness and expedition in performing the orders and commands of God. See on Isaiah 6:2. And they were full of eyes within Bengelius reads κυκλοθεν και εσωθεν γεμουσιν οφθαλμων, round about and within they are full of eyes: round about signifying their attention to and knowledge of the state of the world and church in general; or rather, perhaps, their vigilance and circumspection, their attention to their duty to God and man, and their watchful observance of the designs, wiles, devices, and various motions and snares of their spiritual enemies; and they are said to be full of eyes within, to signify their self-knowledge, their diligent attention to the state of their own hearts, and the various workings of their passions and appetites, their affections and thoughts. And they rest not O happy unrest! day and night They are incessant in the spiritual worship, adoration, and praise of him who is a Spirit; and at all proper opportunities they unite in acts of solemn and external worship; saying With their lips, as well as in their hearts; Holy, holy, holy, Lord God Almighty, which ever was, and now is, and is still to come Or, for ever will be; the one true God, the everlasting Lord, the Supreme Governor of all beings.

There are two words in the original very different from each other, both which we translate holy. The one, οσιος, means properly, merciful: but the other, αγιος, which occurs here, implies much more. “This holiness is the sum of all the praise which is given to the Almighty Creator, for all that he does and reveals concerning himself, till the new song brings with it new matter of glory. This word properly signifies separated. And when God is termed holy, it denotes that excellence which is altogether peculiar to himself; and the glory flowing from all his attributes conjoined, shining forth from all his works, and darkening all things besides itself, whereby he is, and eternally remains, in an incomprehensible manner, separate, and at a distance, not only from all that is impure, but likewise from all that is created. God is separate from all things. He is, and works from himself, out of himself, in himself, through himself, for himself. Therefore he is the First and the Last, the only One, and the Eternal; living and happy, endless and unchangeable, almighty, omniscient, wise and true, just and faithful, gracious and merciful. When God is spoken of, he is often named, The Holy One. And as God swears by his name, so he does also by his holiness, that is, by himself. This holiness is often styled glory; often his holiness and glory are celebrated together, Leviticus 10:3; Isaiah 6:4. For holiness is covered glory, and glory is uncovered holiness. The Scripture speaks abundantly of the holiness and glory of the Father, the Son, and the Holy Ghost. And hereby is the mystery of the Holy Trinity eminently confirmed. That is also termed holy, which is consecrated to him, and for that end separated from other things. And so is that wherein we may be like God, or united to him. In the hymn resembling this, recorded by Isaiah, (Revelation 6:3,) is added, The whole earth is full of his glory. But this is deferred in the Revelation, till the glory of the Lord (his enemies being destroyed) fills the earth.” Wesley.