To see God’s holiness is to see His goodness. Because he is perfect, its pure goodness and is an absolute and perfect measure of the heart. A little evil in one’s heart will be greatly magnified to negative infinity, causing a dispropotionately repentive response – realisation of utter depravity of our soul. This was Isaiah’s response. He was thus totally sold out to God thereafter, to also call others to a similar repentance.
I see His holiness and the train of glory, filling my unclean body, taking my guilt and sin away – he calls and sends, I answer and obey because of His grace and mercy.
Have you seen His glory?
Isaiah 6:1-13 ESV
In the year that King Uzziah died I saw the Lord sitting upon a throne, high and lifted up; and the train of his robe filled the temple.  Above him stood the seraphim. Each had six wings: with two he covered his face, and with two he covered his feet, and with two he flew.  And one called to another and said: “Holy, holy, holy is the LORD of hosts; the whole earth is full of his glory!”  And the foundations of the thresholds shook at the voice of him who called, and the house was filled with smoke.  And I said: “Woe is me! For I am lost; for I am a man of unclean lips, and I dwell in the midst of a people of unclean lips; for my eyes have seen the King, the LORD of hosts!”  Then one of the seraphim flew to me, having in his hand a burning coal that he had taken with tongs from the altar.  And he touched my mouth and said: “Behold, this has touched your lips; your guilt is taken away, and your sin atoned for.”  And I heard the voice of the Lord saying, “Whom shall I send, and who will go for us?” Then I said, “Here I am! Send me.”  And he said, “Go, and say to this people: “‘Keep on hearing, but do not understand; keep on seeing, but do not perceive.’  Make the heart of this people dull, and their ears heavy, and blind their eyes; lest they see with their eyes, and hear with their ears, and understand with their hearts, and turn and be healed.”  Then I said, “How long, O Lord?” And he said: “Until cities lie waste without inhabitant, and houses without people, and the land is a desolate waste,  and the LORD removes people far away, and the forsaken places are many in the midst of the land.  And though a tenth remain in it, it will be burned again, like a terebinth or an oak, whose stump remains when it is felled.” The holy seed is its stump.