四分比丘戒本疏 2.38

2.38

第六、與未受戒人共誦戒。謂合聲同誦佛三藏教也。准《善見》自撰文記同誦不犯也。准律，與弟子授經時，應語云：「我說竟汝說。」若不爾者吉羅。准《多論》第六，若二人俱經利並誦，無犯。准此，但各自作本業，無心合聲即不犯也。堂上唱一切誦時，各自念誦，准即開也。《摩得勒伽》二人合唄吉羅，《多論》第六亦爾。

Sixth: the precept against chanting together with an unordained person. This refers to joining voices in reciting together the teachings of the Buddha's Tripiṭaka. According to the Samantapāsādikā, reciting together texts one has composed oneself incurs no offence. According to the Vinaya, when teaching scriptures to disciples, one should say: 'After I finish speaking, you speak.' If not so, it is a duṣkṛta. According to the sixth fascicle of the Sarvāstivāda-śāstra, if both are proficient in the scriptures and recite simultaneously, there is no offence. According to this, as long as each attends to his own task without the intention to join voices, there is no offence. When chanting 'all recite' in the hall, each silently recites to himself, which according to this is permitted. In the Mātṛkā, two people chanting together in verse is a duṣkṛta; the sixth fascicle of the Sarvāstivāda-śāstra says the same.