Manava Dharmashastra 4.98

4.98

ato'smādutsargakarmaṇaḥ kṛtādūrdhvaṃ parataḥ śuklapakṣeṣu chandāṃsi mantrabrāhmaṇasamudāyātmakānvedānpaṭhet | aṅgāni ca śikṣā yajñasūtravyākaraṇādīni kṛṣṇapakṣeṣu saṃpaṭhet |

After this, he shall diligently read the Vedas during the bright fortnights, and all the subsidiary sciences during the dark fortnights.—(98)

Medhātithi’s commentary (manubhāṣya):
‘After this’—after the ‘Utsarga’ rite has been performed,—subsequently, ‘during the brighter fortnights,’ he shall read the Vedas, which consist of the collection of Mantras and Brāhmaṇas. The ‘subsidiary sciences,’ i.e., the Phonetics, Rituals, Grammar and the rest,—he shall read ‘during the dark fortnights’—(98)

This verse is quoted in Mitākṣarā (on 1.143), to the effect that during the rest of the year, one should study the Veda during the bright fortnights and the Subsidiary Sciences during the dark fortnights;—in Madanapārijāta (p. 95), to the effect that the ‘dismissal’ involved in the Utsarjana ceremony does not mean that its study should be totally abandoned during the rest of the year;—in Puruṣārthacintāmaṇi (p. 298) as laying down the method of study to be adopted after Utsarjana;—and in Smṛticandrikā (Saṃskāra, p. 148).

Comparative notes by various authors
Viṣṇu (30.3).—‘Between the Utsarjana and the Upākarma, one shall carry on the study of the Subsidiary Sciences.’