Above it stood the seraphims…and one cried unto another, and said, Holy, holy, holy, is the LORD of hosts: the whole earth is full of his glory.
Now, because we are dealing with worship, let us consider the joys and delights of the heavenly creatures, the seraphim, around the throne of God….
We know very little about these created beings, but I am impressed by their attitude of exalted worship. They are close to the throne and they burn with rapturous love for the Godhead. They were engrossed in their antiphonal chants, “Holy, holy, holy!”…
The key words then and the keynote still of our worship must be “Holy, holy, holy!”
I am finding that many Christians are really not comfortable with the holy attributes of God. In such cases I am forced to wonder about the quality of the worship they try to offer to Him.
The word “holy” is more than an adjective saying that God is a holy God—it is an ecstatic ascription of glory to the Triune God. WHT071-072
Lord, I come before You this day and cry with the seraphim, “Holy, holy, holy, is the LORD of hosts.” May I always approach You with such an attitude of worship. Amen. 
6:2–5 Attending Him were celestial beings called seraphim, with “four wings for reverence and two for service.” These celebrate the holiness of God and require that God’s servants be cleansed before serving Him.
The vision produced deep conviction of sin in the prophet, then brought him to the place of confession.
2 This is the only biblical passage where heavenly beings are called “seraphs.” It is evident from references in Scripture to angels, archangels, principalities, powers, cherubim, seraphim, and so on, that great variety existed among the heavenly beings created by God. This should occasion no surprise, for the created earth, too, is the scene of great diversity.
The seraphs are bright creatures, for the word means “burning ones”; yet they hide their faces from the greater brightness and glory of the Lord. Matthew 22:30 does not explicitly deny that angels have sex organs, so covering their feet as a euphemism for these cannot be completely ruled out. Covering the feet may also suggest humility.
3 There is no indication of the number of seraphs seen by Isaiah. Many scholars think he was present at an act of worship in the temple, perhaps at the new year, and that the antiphonal singing of the Levitical choir was echoed by the heavenly seraphs of his vision. This is conjectural but cannot be ruled out. The apostle Paul evidently believed that angels are present at Christian worship. It is interesting that the chief passage in which this idea appears (1 Co 11:2–16) deals with veiling and unveiling in the presence of God, referred to also here.
The trisagion, or threefold ascription of holiness (cf. Rev 4:8), has been interpreted in reference to the Trinity since the early fathers. Cautious commentators, including Calvin, are inclined to play this down somewhat. He says (in loc.), “The ancients quoted this passage when they wished to prove that there are three persons in one essence of the Godhead. I do not disagree with their opinion; but if I had to contend with heretics, I would rather choose to employ stronger proofs.” It is best for us simply to say that—in the fuller light of the NT—we can see the aptness of this threefold expression, which also places added stress on the holiness of the heavenly King. We go to the NT for clear Trinitarian teaching and to the OT for hints of it.
The theme of divine holiness is of towering importance in Isaiah (see Introduction, pp. 448–49). This man of God could never forget the disclosure of transcendent purity he encountered when he was called to prophetic service (cf. Eze 1).
The language of fullness, employing the same Hebrew verb (mālēʾ; GK 4848), occurs three times in these verses (vv. 1, 3–4), twice in application to the temple and once to the whole earth. So this passage, insisting as it does on the awesome transcendence of the sovereign God, also emphatically teaches his immanence. His transcendence is not remoteness or aloofness but is known through his presence in his created world and temple. Divine transcendence and immanence are always held in balance in biblical theism. Isaiah himself expresses this later when he says (12:6), “Great is the Holy One of Israel among you.”
The word “glory” (kābôd; GK 3883) is used of God in his manifestation to his creatures. The essence of deity is inscrutable, but something of his glory can be seen if God is pleased to disclose it (Ex 33:17–23; Eze 1:28). The Targum on Isaiah also employs the word in v. 1, with its rendering “I saw the glory of the Lord.” After quoting Isaiah 6:10, John said that Isaiah “saw Jesus’ glory and spoke about him” (Jn 12:41). This NIV rendering takes “his” to be Jesus, which is consistent with the context. This amazing statement is in fact altogether consistent with the high Christology of the NT writers, for Jesus is God incarnate, and the same God is revealed in both Old and New Testaments. This may in fact suggest that John understood the trisagion in Trinitarian terms.
 Tozer, A. W., & Eggert, R. (2015). Tozer on the almighty god: a 365-day devotional. Chicago, IL: Moody Publishers.
 MacDonald, W. (1995). Believer’s Bible Commentary: Old and New Testaments. (A. Farstad, Ed.) (p. 944). Nashville: Thomas Nelson.
 Grogan, G. W. (2008). Isaiah. In T. Longman III, Garland David E. (Eds.), The Expositor’s Bible Commentary: Proverbs–Isaiah (Revised Edition) (Vol. 6, pp. 506–507). Grand Rapids, MI: Zondervan.