Manava Dharmashastra 7.114

Manvarthamuktāvalī 7.114

yasmādamāvāsyā guruṃ hanti, śiṣyaṃ hanti caturdaśī, vedaṃ cāṣṭamīpaurṇamāsyau vismārayataḥ tasmāttā adhyayanādhyāpanayoḥ parityajet|