Ante-Nicene Fathers Volume 5
Cyprian: Epistles XXIX-XXXI
The elders of the church in Rome reply to Cyprian, still dealing with the issue of the lapsed. In some sense, they argue, the fact that so many are demanding to be readmitted to church membership is a sign that perhaps they are not true believers--true believers in circumstances such as this would exercise patience and be willing to do what it takes to uphold the unity of the church. Specifically, they should not be using letters of recommendation from the martyrs/confessors to divide the church on this issue: "For if they say that the Gospel has established one decree, but the martyrs have established another; then they, setting the martyrs at variance with the Gospel, will be in danger on both sides." They have simultaneously rebelled against the Gospel and undone the good work of the martyrs by opposing them to the Gospel. The reality of course is that it is these aggressive lapsed who are wrong, not the Gospel or the martyrs. This issue needs to be left to the elders and the church, and not decided by a single faction--not even so blessed a faction as that of the martyrs.
With that said, this does not mean we should totally reject the lapsed. Charity and mercy must be our goal in all things. Having lapsed is a cancer that takes long to cure, not a 24 hour bug that is fixed overnight. If they truly desire to be restored they will understand that and work towards the unity of the church, rather than demanding some imagined rights that they in truth gave up when they betrayed the Gospel of Christ.
This is followed by Epistle XXX, in which the Roman elders emphasize the great sin of apostasy, and how much worse it is than never having believed in the first place. As a result, we as a church need to be careful to guard against it, and protect our own congregations against this sin's encroachment. This includes thinking carefully about how to deal with the lapsed who repent. The best way to decide this may be to call an assembly "with bishops, presbyters, deacons, and confessors, as well as with the laity who stand fast." In other words, the church (not just the elders).
Through all of this, we must continue to pray--both for the lapsed, "that they may be raised up," and for the faithful, "that they may not be temped to such a degree as to be destroyed." In other words, thoughtfulness and discipline should never eliminate mercy and care. The greatness of the sin is in no way greater than the forgiveness that comes through Christ, and there is healing in the Gospel declared by the church in Word and sacrament.
Epistle XXXI is from Cyprian asking the elders in Carthage to be sure to pass Rome's letters on to him, and his letters back to them.