Manava Dharmashastra 2.199

2.199

nodāharennoccārayedasya gurornāma, kevalaṃ upādhyāyācāryabhaṭṭādyupapadarahitaṃ, parokṣamapi | na caivāsyānukurvīta sadṛśaṃ na kuryānnāṭyakāra iva | gatiḥ-evamasmadgururapakrāmati | bhāṣitaṃ-drutavilambitamadhyamatvādi | ceṣṭitam-evaṃ suṅge evamuṣṇīṣaṃ badhnāti evaṃ parivartata ityādi | upahāsabuddhyā'yamanukaraṇapratiṣedhaḥ |

Medhātithi’s commentary (manubhāṣya):
‘When the teacher has his face averted,’—the pupil should sit facing him; that is, if the Teacher happen to have his face turned the other way when he gives his directions, the pupil should go over to the side facing the teacher and then do the aforesaid (listening and conversing).