Revelation 1:8, 22:13
We begin our look at Christ using the most expansive words he spoke about himself. From these words we derive our belief in the cosmic Christ, universal in his excarnate and incarnate person and work. The words he spoke to John open and close the Book of Revelation, framing the letter’s message…and our faith.
‘Alpha and Omega’ is a phrase of height, depth, width, length, breadth, and time. It means all-encompassing. In the Gospel of Thomas, Jesus said this himself, “Split a piece of wood, and I am there. Lift up the stone and you will find me there” (saying 77). 
John was soaking all this up as he followed the incarnate Christ (Jesus) all the way through to his experience of the excarnate Christ on Patmos. His gospel and four letters (1,2,3 John and Revelation) reveal the universal Christ. And so we sing that Christ is “so high we can’t get over him, so low we can’t get under him, so wide we can’t get around him.” Once we see him in his glory, we do not want to.
 James M. Robinson, ed , ‘The Nag Hammadi Library,’ revised edition (HarperSanFrancisco, 1988), 135.