I John 1  I love John's testimony here... we heard, we saw, we beheld, we touched.. the "Word of Life".  We had "fellowship" with God the Father and with Jesus Christ, His Son.  Fellowship - koinonia - communion, partnership;  John shared life with the Giver of Life and now it brings him great joy to pass these truths on to others.

Where he starts is a bit surprising.. " God is light and in Him there is no darkness at all." 
We would expect something like.."God is the Creator" or God is the King of the Universe", "God is the Judge" or "God is love..."
But,  John starts with this bold statement.. " God is light.. " God is phōs- manifest, shine, luminousness, fire, light.... and "in Him there is no darkness at all" -  no dimness, no obscurity, no shadiness..

And, those who say we are in partnership with Him, cannot walk with Him unless we also "walk in the light". .. cleansed from all sin by the "blood of Jesus His Son".  If we deny the darkness, saying we have no sin.. we are liars.  If we "confess our sins He is faithful and righteous to forgive us our sins and to cleanse us from all unrighteousness."  

God will forgive us when we are honest about the darkness that hides in our souls.  He is Light and He will shine so that the darkness is overcome.  What a wonderful Savior and God we serve.  He sends our sins away.. further than the east is from the west.  Hallelujah!

Father in heaven, we bow before You and exalt Your Holy name. You are Light and You have sent the Light of the World, Your only Begotten Son, Jesus, to pay the price for our sins.  Thank You. Fill us with Your Light, always for we want to live in fellowship with You forever. Amen.