Our Scripture reading today is Isaiah 6:1-4.
Verse 3, "And one cried unto another, and said, Holy, holy, holy, is the LORD of hosts: the whole earth is full of his glory."
The seraphims give us an example to follow as we give our worship to the only One Who is worthy.  The One Who is worthy is Father, Son and Holy Ghost.  This shows us the purpose for the three times the seraphims said "holy".  Another reason for repeating is that in the Hebrew language emphasis and intensity are given each time something is repeated.  In this verse, we are reminded there in none holy like our God!  He is set apart from His creation.  He is Divine!
Isn't is amazing that the thrice holy God created us to be compatible with and have communion with Him.  We are made in His image.  Genesis 1:27, "So God created man in his own image, in the image of God created he him; male and female created he them."  The creator God made a way that we could have eternal fellowship with Him and this fellowship did not have to wait until Heaven.  Once the shed blood of Jesus Christ is applied to our sin debt, we are forgiven forever and given direct access to the Father.  We can enter into His presence and like the seraphims can say. "Holy, holy, holy, is the LORD of hosts: the whole earth is full of his glory".
Let that sink in and it will minister to you all day long.