Nicene and Post-Nicene Fathers, Vol. IV:
Writings in Connection with the Donatist Controversy.: Chapter 67

Chapter 67.—149.  Petilianus said:  "‘Blessed are the merciful:  for they shall obtain mercy.’  But how shall I call you merciful when you inflict punishment on the righteous?  Shall I not rather call you a most unrighteous communion, so long as you pollute souls?"

150.  Augustin answered:  You have proved neither point,—neither that you yourselves are righteous, nor that we inflict punishment on even the unrighteous; and yet, even as false flattery is generally cruel, so just correction is ever merciful.  For whence is that which you do not understand:  "Let the righteous smite me, it shall be a kindness; and let him reprove me"?  For while he says this of the severity of merciful correction, the Psalmist immediately went on to say of the gentleness of destructive flattery, "But the oil of sinners shall not break my head." 2161   Do you therefore consider whither you are called, and from what you are summoned away.  For how do you know what feelings he entertains towards you whom you suppose to be cruel?  But whatever be his feelings, every one must bear his own burden both with us and with you.  But I would have you cast away the burden of schism which you all of you are bearing, that you may bear your good burdens in unity; and I would bid you mercifully correct, if you should have the power, all those who are bearing evil burdens; and, if this be beyond your power, I would bid you bear with them in peace.

Footnotes

Ps. cxli. 5, LXX., cf. Hieron.