What is the offense of breaking the sangha?

Breaking the Saṅgha includes destroying a monastic community (saṅgha) as well as monks who are not within a monastic community. A group composed of four or more monastics is called a monastic community (saṅgha), and these four monastics must all be monks who have received full ordination (upasaṃpadā) and possess the monastic precept-substance. If strife is stirred up within a monastic community until only three monks remain, it no longer constitutes a monastic community, and thus the saṅgha is dispersed. Those who cause a monastic community to break apart through strife have committed the offense of the Avīci hell, and at the end of their lives they will incur the retribution of the Avīci hell.

Monastics numbering fewer than three, although they cannot be called a monastic community, are still called the monastic assembly (saṅgha). If one also stirs up conflicts and disputes among them, sowing discord and estrangement, this is called disrupting the monastic assembly, and the offense is likewise a hellish offense. When one monastic leads a group of disciples, although they cannot form a monastic community, if the role this monastic plays for Buddhism is also quite significant, then sowing discord between the master and the disciples, splitting apart the teacher-disciple relationship, constitutes a very grave offense as well. If this monastic holds an especially exceptional position, wielding a pivotal influence on the future and development of Buddhism, and also has great power to gather and guide sentient beings, and someone slanders such a monastic and splits apart their disciples, then this offense is extremely, extremely grave—greater than the offense of destroying other monastic communities, and certainly it is an offense leading to the Avīci hell.