Manava Dharmashastra 4.99

4.99

yatra varṇasvarābhivyaktiḥ sphuṭā na bhavati tadavispaṣṭam | tacca drutāyāṃ vṛttau prāyeṇa bhavati | niśānte paścimarātribhāge | suptotthito yadā'dhīyīta punaḥ śrāmyettadā na śayīta | "na niśānte pariśrānto brahmādhītya śayota tu" evaṃ yuktaḥ pāṭhaḥ |

Medhātithi’s commentary (manubhāṣya):
‘Indistinct’—when the letters and accents are not clearly pronounced. This happens when a man is reciting hurriedly.

‘At the end of night’— in the latter part of night. If he, on rising from sleep, study the Veda, he shall not, if he becomes tired, go to sleep again. The right reading is—‘na niśānte pariśrānto brahmādhītya śayīta tu.’—(99)