四分律刪補隨機羯磨 1.34

1.34

(In the Vinaya the Buddha said: “There are four kinds of saṃghas: first, a four-person saṃgha, which may perform all karman procedures except ordination, pravāraṇā, and āvarjana; second, a five-person saṃgha, which [may perform all] except ordination and āvarjana in the central region; third, a ten-person saṃgha, which [may perform all] except āvarjana; fourth, a twenty-person saṃgha, which may perform all karman procedures, and even more so if exceeding twenty. If it lacks one person, it is contrary to the Dharma, contrary to the Vinaya, and invalid.”)