Isaiah 6:3

Holy, Holy, Holy appears in the Bible two times. Once in the Old Testament- Isaiah 6:3 and once in the New Testament- Revelation 4:8. Isaiah (author of the book by the same name) and John (author of The Book of Revelation), while caught up in the Spirit, experienced very similar visions. Both had different reactions. Isaiah terrified because he, a sinner, was in the throne room of the God Almighty, Creator of the universe and he was "unclean". John, the disciple whom Jesus loved, had a slightly different reaction. He had walked with Jesus, stood at His feet when He died, saw Him after His resurrection and finally, witnessed His ascension. He knew and understood that the blood of Jesus made him "clean". 

We as believers can approach the throne of The Lord God Almighty because we have been made "clean". 

Holy, holy, holy
Lord, God Almighty
Early in the morning our song shall rise to Thee

Holy, holy, holy
Merciful and mighty
God in three persons blessed Trinity

Holy, holy, holy
Though the darkness hide Thee
Though the eye of sinful man thy glory may not see

Only Thou art holy; there is none beside Thee
Perfect in power, in love, and purity

Holy, holy, holy
Lord, God Almighty
All Thy works shall praise Thy name in earth and sky and sea
Holy, holy, holy
Merciful and mighty
God in three persons blessed Trinity