大比丘三千威儀 1.54

1.54

不應作禮有五事：一者若讀經若持經，不應為上座作禮；二者上座在下處、自在高處，不應作禮；三者上座在前若已去，不應從後作禮；四者不得座上為上座作禮；五者不得著帽為佛作禮。若三師比丘僧上座，其罪重。

There are five matters where one should not pay homage: first, whether reciting sūtras or holding sūtras, one should not pay homage to a sthavira; second, when the sthavira is in a lower place and oneself is in a higher place, one should not pay homage; third, when the sthavira is in front or has already walked past, one should not pay homage from behind; fourth, one must not pay homage to a sthavira while remaining on one's seat; fifth, one must not pay homage to the Buddha while wearing a cap. If [done to] the three masters, the bhikṣusaṅgha, or a sthavira, the offense is grave.