梵網經菩薩戒本疏 5.67

5.67

初、制意者，一、為欲護前說、謗、毀等三重戒故；二、為離惱亂諸好人故；三、為護佛法離醜惡故，實尚不說，況起謗耶？四、為離自招重業過故。

First, the rationale for establishment: 1. In order to protect the earlier three major precepts against speaking of [faults], slandering, and reviling; 2. In order to avoid distressing and troubling good people; 3. In order to protect the Buddha-Dharma and keep it free from ugliness—even the truth should not be spoken of, how much less giving rise to slander? 4. In order to avoid personally incurring the fault of heavy karma.