As believers, sons and daughters of an absolutely Holy God, our call to holiness is inextricably linked to the Holiness of the God we worship.”As obedient children, do not be conformed to the passions of your former ignorance, but as he who called you is holy, you also be holy in all your conduct, since it is written, “You shall be holy, for I am holy.” 1Pe 1:14 -16
Isaiah saw the Seraphim around the throne of God and they cried out “Holy, holy, holy is the LORD of hosts; the whole earth is full of his glory!” Isa 6:3
“Woe to me!” I cried. “I am ruined! For I am a man of unclean lips, and I live among a people of unclean lips, and my eyes have seen the King, the LORD Almighty.” (Isa 6:1,5).
Why did Isaiah cried out like that? Prophet Isaiah, viewed as righteous man of virtues in Israel, was given a view of an absolutely Holy God. In his classic book “The Holiness of God”, Dr R.C. Sproul described it vividly, “In that single moment, all his self-esteem was shattered. In a brief second he was exposed, made naked beneath the gaze of the absolute standard of holiness. As long as Isaiah could compare himself to other mortals, he was able to sustain a lofty opinion of himself to other mortals, he was able to sustain a lofty opinion of his own character. The instant he measured himself by the ultimate standard, he was destroyed – morally and spiritually annihilated. He was undone. He came apart, His sense of integrity collapsed.”
“Hence that dread and amazement with which as Scripture uniformly relates, holy men were struck and overwhelmed whenever they beheld the presence of God. When we see those who previously stood firm and secure so quaking with terror, that the fear of death takes hold of them, nay, they are, in a manner, swallowed up and annihilated, the inference to be drawn is that men are never duly touched and impressed with a conviction of their insignificance, until they have contrasted themselves with the majesty of God.” John Calvin, Institutes on the Christian Religion 1, part 5 Book First: Of the Knowledge of God the Creator
“The Holiness of God: The angels declare that God is “Holy, Holy, Holy.” Without a proper grasp of God’s holiness we do not understand who He truly is, nor do we understand who we truly are. Once we begin to grasp the true meaning of God’s holiness, our lives and our worship will be forever changed.” Source: http://www.ligonier.org/
Read more here : The Holiness of God