大比丘三千威儀 1.30

1.30

澡嗽有五事：一者不得蹲、二者不得向佛塔亦莫背、三者不得向和上阿闍梨諸師亦莫背、四者不得於瀆上若淨地、五者不得中與人共語亦莫受人禮。

In washing and rinsing the mouth, there are five matters: first, one must not squat; second, one must neither face toward the Buddha stūpa nor turn one's back to it; third, one must neither face toward the upādhyāya, ācārya, and other masters nor turn one's back to them; fourth, one must not do so over a ditch or upon clean ground; fifth, midway through, one must not converse with people, nor should one accept bows from people.