Manava Dharmashastra 2.196

2.196

āsīnasya sthitaḥ kuryād abhigacchaṃs tu tiṣṭhataḥ
pratyudgamya tv āvrajataḥ paścād dhāvaṃs tu dhāvataḥ //

Let him do (that), standing up, if (his teacher) is seated, advancing towards him when he stands, going to meet him if he advances, and running after him when he runs;