And the four living creatures ... never cease to say,
"Holy, holy, holy, is the Lord God Almighty, who was and is and is to come!"
"Holy, Holy, Holy"
St. John's Revelation brings us a picture of the throne room of Heaven. Surrounding God's throne, four living creatures worship God, singing as we do, "Holy, holy, holy, Lord God Almighty, all Thy works shall praise Thy name in earth and sky and sea" (LSB #507.4).
That's the point of creation. "The heavens declare the glory of God" (Psalm 19:1). The Psalms are filled with encouragement for all God's works to praise Him. Because that is what Heaven is--one eternal worship service, praising God for everything He has done.
Of course, the biggest thing that God has done is give us salvation. We sing "Holy, Holy, Holy" because He has made us holy by giving us the perfect life, death and resurrection of Jesus and everything that He has accomplished for us. You have been declared holy by God because Jesus died for you. Think about that as you praise God for how holy He is. Amen.