While most first and second generation reformers did not explicitly enumerate discipline as a mark of the church, they nevertheless attested to its place as an essential function of a healthy church. As Martin Bucer (1491-1551) argues in this excerpt from his work on the care of souls, in order to shepherd their congregants, pastors must ensure that proper order is maintained and true repentance brought about.
True Pastors Are Diligent in Discipline
Therefore, when there are true shepherds and physicians of souls in the church and the churches are well and properly ordered, they will never remain silent concerning these hurts and wounds to the inner being, which they learn of in the sheep of Christ, letting them carry on without penance, but when gentleness does not move such people to repent, they will like St. Paul no longer spare them, but will show the power of Christ and employ drastic measures to bring about the humiliation and mortification of the sinful flesh and require some significant proof of sorrow and intention to mend their ways. For such shepherds and caregivers of souls are true servants of Christ in the care of souls and the pastoral ministry, and are recognized as such by the churches. Will not the Spirit of Christ therefore work and act in them as well as he worked and acted in St. Paul, and as he also ordered and commanded his ancient and coarser people?
True Care of Souls.
1 Corinthians, ed. Scott M. Manetsch. Reformation Commentary on Scripture, NT vol. 9a, p. 92.