From a letter to a monk named Adam:
If you remain yet in that spirit of charity which I either knew or believed to be with you formerly, you would certainly feel the condemnation with which charity must regard the scandal which you have given to the weak. For charity would not offend charity, nor scorn when it feels itself offended. For it cannot deny itself, nor be divided against itself. Its function is rather to draw together things divided; and it is far from dividing those that are joined. Now, if that remained in you, as I have said, it would not keep silent, it would not rest unconcerned, nor pretend indifference, but it would without doubt whisper, with groans and uneasiness at the bottom of your pious heart, that saying, Who is offended, and I burn not (2 Cor. xi. 29). If, then, it is kind, it loves peace, and rejoices in unity; it produces them, cements them, strengthens them, and wherever it reigns it makes the bond of peace. As, then, you are in opposition to that true mother of peace and concord, on what ground, I ask you, do you presume that your sacrifice, whatever it may be, will be accepted by God, when without it even martyrdom profiteth nothing (1 Cor. xiii. 3)? Or, on what ground do you trust that you are not the enemy of charity when breaking unity, rending the bond of peace, you lacerate her bowels, treating with such cruelty their dear pledges, which you neither have borne nor do bear? You must lay down, then, the offering, whatever it may be, which you are preparing to lay on the altar, and hasten to go and reconcile yourself not with one of your brethren only, but with the entire body. The whole body of the fraternity, grievously wounded by your withdrawal, as by the stroke of a sword, utters its complaints against you and the few with you, saying: The sons of my mother have fought against me (Cant. i. 5). And rightly; for who is not with her, is against her. Can you think that a mother, as tender as charity, can hear without emotion the complaint, so just, of a community which is to her as a daughter? Therefore, joining her tears with ours, she says, I have nourished and brought up children, and they have rebelled against me (Isa. i. 2).
Charity is God Himself. Christ is our peace, who hath made both one (Eph. ii. 14). Unity is the mystery even of the Holy Trinity. What place, then, in the kingdom of Christ and of God has he who is an enemy of charity, peace, and unity?