Śatapatha Brāhmaṇa ("of a hundred paths") 11.5.7.3

11.5.7.3

yadyaddha vā ayaṃ candasaḥ svādhyāyamadhīte tena-tena haivāsya yajñakratuneṣṭam bhavati ya evaṃ vidvāntsvādhyāyamadhīte tasmātsvādhyāyo'dhyetavyaḥ

And, verily, whatever portion of the sacred poetry (khandas) he studies for his lesson with that sacrificial rite, offering is made by him who, knowing this, studies his lesson: therefore one's (daily) lesson should be studied.