Cyprian: Epistles XV-XIX
In Epistle XV, Cyprian writes to believers in prison for confessing the faith. he reminds them that what they have is more than the mightiest and most glories powers of the earth could ever comprehend--friendship with God.
Now, therefore, let magistrates and consuls or proconsuls go by; let them glory in the ensigns of their yearly dignity, and in their twelves fasces. Behold, the heavenly dignity in you is sealed by the brightness of a year's honor, and already, in the continence of its victorious glory, has passed over the rolling circle of the returning year. The rising sun and the waning moon enlightened the world; but to you, He who made the sun and moon was a greater light in your dungeon, and the brightness of Christ glowing in your hearts and minds irradiated with that eternal and brilliant light the gloom of the place of punishment, which to others was so horrible and deadly.Cyprian then asks that they pray for him, which in Epistle XVI they respond that he is in their thoughts.
Epistle XVII returns to the question of restoring the repentant lapsed. Cyprian says that repentance and humility are necessary for all of us, including them, and that we ought to account for the recommendation of those who went to prison for the faith in restoring those who apostatized rather than suffer persecution, but that at the end of the day this "matter... waits for the counsel and judgment of all of us." Consequently, Cyprian does not "dare to prejudge and so to assume a common cause for my own decision." He may have meant he was waiting for a Council or Synod to make a decision, or he may have meant that the congregation was to decide. I like to think it's the latter, but I suspect it's the former.
Epistle's XVIII and XIX are a back-and-forth between one Caldonius and Cyprian. In XVIII, Caldonius asks what to do with a few people who had been believers who were disciplined for rejecting the faith but may not have actually done so. (One woman, "Bona," made a sacrifice to the gods--a sign of NOT being a Christian--only when physically dragged there by her husband, claiming all the way 'I did not do it!" and presumably unwilling at every point.) Caldonius asks Cyprian what ought to be done when such individuals petition for readmission to the membership of the church. Cyprian replies that they ought to be restored, given their confession and their clear contrition and the apparent working of grace in their lives. Cyprian then refers Caldonius to a book he has written on this topic.