Ante-Nicene Fathers Volume 5
Cyprian: Epistles XX-XXII
Epistles XX and XXI are not from Cyprian at all, but rather are from Celerinus of Rome to Carthage, and from Lucian (presumably in Carthage, and at least in North Africa) back to Celerinus.
Celerinus writes to those who are in prison for confessing Christ to ask them to pray for his sister, who had identified as a Christian but "in this time of devastation has fallen from Christ; for she has sacrificed [to the gods] and provoked our Lord."
In reply, Lucian does not respond to the direct request other than to apologize for the delay in writing (the church was being persecuted, after all--though peace is now being restored) and to note that he and the other believers are greatly sorrowed by the defection. The implication, however, is that the petition has been granted--which in fact we know for a fact from the next letter.
Epistle XXII is from Cyprian and includes the other two, and notes that Lucian had acted alone and without the authorization of the elders or of the Christians currently suffering in prison. The letters Lucian sent were both unauthorized and too broad in scope, and now have large numbers of people clamoring to be restored (or even admitted for the first time) to the full fellowship of the church, despite there as yet being no clear decision on what to do in some cases, and the clear need for division between the church--"martyrs are made by the Gospel," after all--and the world.