梵網經菩薩戒本疏 5.49

5.49

就初戒中制意者，菩薩理應和諸違諍令息相害，而反通國使令相侵害，為失之甚故須制也。別說有三：一、生譏嫌故；二、乖和行故；三、成相殺故。為過既重，理宜須制。

Regarding the rationale for establishment in the first precept: A bodhisattva in principle should harmonize conflicts and disputes to make mutual harm cease; but on the contrary, to act as an envoy communicating between states to make them invade and harm one another is an extreme fault, and therefore it must be prohibited. Specifically, there are three reasons: 1. Because it gives rise to ridicule and suspicion; 2. Because it runs counter to the practice of harmony; 3. Because it brings about mutual killing. Since the fault is grave, it ought in principle to be prohibited.