And he said, Draw not nigh hither: put off thy shoes from off thy feet, for the place whereon thou standest is holy ground.
I will endeavor to discuss the holiness of God, the Holy One. We cannot comprehend it, and we certainly cannot define it.
Holiness means purity, but “purity” doesn’t describe it well enough. Purity merely means that it is unmixed, with nothing else in it. But that isn’t enough. We talk of moral excellency, but that isn’t adequate. To be morally excellent is to exceed someone else in moral character. But when we say that God is morally excellent, who is it that He exceeds? The angels, the seraphim? Surely He does—but that still isn’t enough. We mean rectitude; we mean honor; we mean truth and righteousness; we mean all of these—uncreated and eternal….
Language cannot express the holy, so God resorts to association and suggestion. He cannot say it outright because He would have to use words for which we know no meaning….
God cannot tell us by language, so He uses association and suggestion and shows how holiness affects the unholy. He shows Moses at the burning bush before the holy, fiery Presence, kneeling down to take his shoes from his feet, hiding his face, for he was afraid to look upon God. AOG159-160
Lord, I don’t often stop to contemplate the reality of Your holiness. Give me a glimpse of Your holiness today, even if I have to hide my face in fear. Amen. 
3:5 The Lord promised Moses that He would deliver His people from Egypt and bring them into a land of abundance—that is, Canaan—inhabited by the six heathen nations listed in verse 8. The word “holy” occurs here for the first time in the Bible. By removing his sandals, Moses acknowledged that the place was holy.
5–6 God’s presence demands a holistic preparation of the one who aspires to enter his presence. To teach Moses this lesson, God sets up admittedly arbitrary boundaries—“Do not come any closer”—and commands that he should also remove his sandals (v. 5). This is to prevent him from rashly intruding into God’s presence and to teach him that God is separate and distinct from mortal human beings (cf. 19:10–13; 2 Pe 1:18). Because God is present, what has been ordinary becomes “holy ground” and consequently “set apart” for a distinct use. The place where sheep and goats traveled just a short time ago is transformed into “holy ground” by God’s presence. As Bush observes (Exodus, 1:44), it is not an intrinsic holiness because of the nature of the ground itself but relative only to and based on the divine appointment that remains true as long as God ordains it so. This also is the first occurrence of the noun “holy” in Scripture (cf. Ge 2:3 for the verbal form).
When the condition for meeting God is satisfied, the Lord reveals himself. He identifies himself as the “God of your father” (v. 6; collective singular—see Ge 26:24; 31:5, 42, 53; 43:23; 46:1, 3; 49:25; 50:17; Ex 15:2; 18:4 for a similar formula). Of course, the plural form “God of your fathers” appears more frequently (cf. also Stephen’s use of the plural in Acts 7:32), but the collective singular also has a special point in that it is through the one man of promise (ultimately, the Messiah himself) that the many are to receive God’s blessing. Thus God assures Moses that the God of his father has not forsaken his repeated word of promise (Ge 15:1–21; 26:2–5; 35:1–12) or his people, and he will certainly be with Moses in the commission he is about to receive. (On Moses’ fear of “looking” at God, see comment on 24:9–10.)
 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. 91). Nashville: Thomas Nelson.
 Kaiser, W. C., Jr. (2008). Exodus. In T. Longman III & D. E. Garland (Eds.), The Expositor’s Bible Commentary: Genesis–Leviticus (Revised Edition) (Vol. 1, p. 365). Grand Rapids, MI: Zondervan.