Polycarp writes concerning a couple that used to be presbyters (or overseers) in the Philippian church.
"I am greatly grieved for Valens, who was once a presbyter among you, because he so little understands the place that was given him [in the Church]. I exhort you, therefore, that ye abstain from covetousness, and that ye be chaste and truthful. 'Abstain from every form of evil.' For if a man cannot govern himself in such matters, how shall he enjoin them on others? If a man does not keep himself from covetousness, he shall be defiled by idolatry, and shall be judged as one of the heathen." (Polycarp 11)It is unclear exactly what his sin was but many believe that is was incontinence which is a polite way of saying sexual immorality. This could be why Polycarp urges the rest of the church to remain "chaste" and "truthful." It appears that, because of his sin, he was no longer in fellowship with the church and was subject to the judgments of those who were "outside". Polycarp goes on to affirm that such a stain of sin was not cast over the entire church but rather just upon one member.
"I have neither seen nor heard of any such thing among you, in the midst of whom the blessed Paul laboured, and who are commended in the beginning of his Epistle. For he boasts of you in all those Churches which alone then knew the Lord; but we [of Smyrna] had not yet known Him." (Polycarp 11)It is important that the church be pure, that there be a contrast between then holy and the profane. If sin pervades the church then how will the sins of others stand in contrast to the purity of the rest. If the church is just like the world then how will separation from the church testify of the sinfulness of the one excluded? Separation from the church should be a visible representation of the separation from the truth that the sinner has chosen for themselves. While "we all stumble in many ways," (James 3:2) the church must never become a place where we shelter the practice of habitual sin.
Finally, Polycarp encourages the church not to be too harsh on the one who had sinned and to be willing to receive them back should they repent.
"I am deeply grieved, therefore, brethren, for him (Valens) and his wife; to whom may the Lord grant true repentance! And be ye then moderate in regard to this matter, and 'do not count such as enemies,' but call them back as suffering and straying members, that ye may save your whole body. For by so acting ye shall edify yourselves." (Polycarp 11)Our goal in the church should be that all should be saved and that none should be lost. Should someone stray from the truth, we should not "write them off" but rather continue to love them, pray for them, and call them back to the truth. Even if they should sin, they are still our family, our brothers and sisters, and we should rather that they return in repentance then be lost in their sins. We must let our compassion rule over our desire for judgment, desiring their restoration more than the receiving of their just deserts.