Vasishthadharmasutra 11.48

11.48

vijñāyate hi | tribhirṛṇairṛṇavānbrāhmaṇo jāyate | yajñena devebhyaḥ prajayā pitṛbhyo brahmacaryeṇa ṛṣibhya ityeṣa vānṛṇo yajvā yaḥ putrī brahmacaryavāniti

For it is declared in the Veda, 'A Brâhmana is born, loaded with three debts,' (and further, 'He owes) sacrifices to the gods, a son to the manes, the study of the Veda to the Rishis; therefore he is free from debt who has offered sacrifices, who has begotten a son, and who has lived as a student (with a teacher).'