大比丘三千威儀 1.73

1.73

有五事不應用坐：一者眾坐時；二者入城時；三者九十日竟時；四者與三師同處為恭敬；五者至白衣家若客舍，皆不應獨自一室中，安隱時得用作私匿。

There are five matters where it should not be used for sitting: first, when sitting in the assembly; second, when entering a city; third, when the ninety days [of the retreat] are completed; fourth, out of reverence when in the same place as the three masters; fifth, when going to the home of a white-robed layperson or to a guesthouse—in all these cases, one should not be alone in a single room; [only] in times of safety and quietude may it be used for personal privacy.