A monk’s “purity” is lost when he incurs an offense, but he can restore his purity by confessing and making amends appropriate to that class of offense. All monks on site must profess their purity before The Prātimokṣa Sūtra is recited during the restoration rite. If a monk cannot attend, he must profess his purity through a proxy, who conveys it to the saṅgha. See Kalyāṇamitra (F.318.a–b).