釋氏要覽 3.192

3.192

僧祇云。若他禮佛。誦經。寫經。授經時。並不得禮。又云。禮人不得對佛。又夜闇僻處不得禮。人恐涉嫌疑○五分律云。相瞋人不得於屏處禮拜○四分律云。飲食。敢果。說法。漱口。嚼楊枝。剃髮。裸身。大小行時。並不得禮。

The Mahāsāṃghika says: 'When another person is bowing to the Buddha, reciting sūtras, copying sūtras, or teaching sūtras, one must not bow to them in any of these cases.' It also says: 'When bowing to someone, one must not face the Buddha. Furthermore, in dark or secluded places, one must not bow to people, for fear of incurring suspicion.' The Mahīśāsaka-vinaya states: 'People harboring mutual anger must not bow or prostrate in hidden places.' The Dharmaguptaka-vinaya states: 'When eating, chewing fruit, explaining the Dharma, rinsing the mouth, chewing a tooth-stick, shaving the head, being naked, or during urination or defecation, in none of these cases may one bow.'