In the second century an unknown Christian wrote a letter to his pagan friend Diognetus to explain to him why Christians are different and how God has both delivered them from sin and brought them to eternal life through the death and resurrection of Jesus Christ, His Son.

No man living has ever seen God or known Him; it is He Himself who has given us the revelation of Himself.  But He has only revealed Himself to faith, by which alone are we permitted to know God. For God, though Lord and Architect of the whole world, who made and set in order each single thing that is, was something more than loving towards mankind: He was long-suffering as well.  So He has always been, and is still, and ever shall be: merciful, kind, slow to anger, and true; there is none so good as He.   

How surpassing is the love and tenderness of God!  In that hour, instead of hating us and rejecting us and remembering our wickedness against us, He showed how long-suffering he is.  He bore with us, and in pity He took our sins upon Himself and gave His own Son as a ransom for us – the Holy for the wicked, the Sinless for the sinners, the Just for the unjust, the Incorrupt for the corrupt, the Immortal for the mortal.  For was there, indeed, anything except His righteousness that could have availed to cover our sins?  In whom could we, in our lawlessness and ungodliness, have been made holy, but in the Son of God alone?  O sweet exchange! O unsearchable working! O benefits unhoped for! – that the wickedness of multitudes should thus be hidden in the holy One, and the holiness of One should sanctify the countless wicked!

In times past, He convinced us that our human nature by itself lacked the power of attaining to life; today, He reveals to us a Saviour who has power to save even the powerless.  The purpose behind both of these acts is that we should believe in His goodness, and should look on Him as our Nourisher, Father, Teacher, Counsellor, Healer, Wisdom, Light, Honour, Glory, Power, and Life, and have no anxiety about our clothing or our food.   Through Him the Church is enriched; abounding Grace is multiplied among the saints, furnishing understanding, revealing mysteries, proclaiming times and seasons, and rejoicing over the faithful believers – the Grace which is granted to every seeker who does not violate his vows of faith, or transgress the bounds fixed by the Fathers. 

Grieve not this Grace, and then you shall understand the things which the Word, when it is His will to do so, imparts through the lips of those he chooses.  For whatsoever that commanding will of the Word impels us to utter, we are at pains to communicate to you, in our love for the truths He has revealed to us.  

Letter to Diognetus (2nd century)