Here is what the early church fathers said about sin:

• Mathetes  130 AD
• Epistle to Diognetus 5 - Christians follow the customs of their native lands in regard to marriage, food, clothing, and conduct. They marry and have children but they never have abortions. They obey all the laws of their country.
• Epistle to Diognetus 11 - He (Mathetes) was taught directly by the apostles. Jesus is uncreated (from everlasting)
   
• Justin Martyr 165 AD
• Dialogue 88 - Men and angels have free will. The human race, which from Adam had fallen under the power of death and the guile of the serpent, so that each one of us has committed personal transgression. 
   
• Tatian 166 AD
• Greeks 17 - Demons use numbers, letters, roots, and amulets to ensnare people.
• Greeks 18 - Demons use medicine also (he dose not believe taking medicine could cure anyone. we should rely on God alone.)
   
• Irenaeus 177 AD
• Against Heresies 4.14 - If you do not observe the Decalogue (natural law) you have no salvation. 
   
• Clement of Alexandria 192 AD
• Instructor 1.13 - Everything contrary to right reason is sin.
• Instructor 2.1 - Avoid over eating (begins to get slightly ascetic)
• Instructor 2.5 - People who by their actions or speech seem to be senseless should be removed from the congregation.
• Instructor 2.6 - Christians don't use obscene language, mocking words or looks, slander, or joking that may lead to anger. (start getting legalistic on dress, manors and customs.)
• Instructor 2.13 - Guard against excessive use of jewelry.
• Instructor 3.11 - Wearing gold and fine clothes is ok, if clean and are not taken too far.
• Stromata 2.12 - Repentance is torturing yourself for your sins. 
• Stromata 2.13 - If you sin again after the second repentance it proves you are not truly repentant. he quotes Hebrews 10, sin willfully (if taken too far it contradicts Romans 7) he is probably thinking of a hypocrite or someone apostatizing and coming back to the church several times. 
• Stromata 2.14 - Involuntary sins should not be punished. 
• Stromata 2.15 - There are three kinds of sin. A mistake, which is done in ignorance. (hurting someone by mistake, this sin is never imputed so there is no need for repentance or forgiveness) A sin, which is doing something for your own pleasure, it must be repented of or God will chastise you ( ie. sex or drunkenness. Compare to Hebrews 13). And a crime, which is trying to hurt some one or fight against God's kingdom. (ie. sacrilege or murder) He quotes Jesus as "on these two commandments hang all of the law and prophets, and are suspended." 
• Stromata 4.24 Christians teach all is forgiven when you repent. God would only chastise to teach you to repent. You do not have to pay for your sin. 
   
• Lactantius 285 AD
• Divine Institutes 2.19 - Christians do not bow to Images.
• Divine Institutes 3.18 - Suicide is a sin. Gives example of the pagan philosophers who are board with life.
• Divine Institutes 6.13 - There are unknown sins.

More to Come!