Bhagavatapurana 5.9.4

5.9.4

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tasyāpi ha vā ātmajasya vipraḥ putra-snehānubaddha-manā āsamāvartanāt saṃskārān yathopadeśaṃ vidadhāna upanītasya ca punaḥ śaucācamanādīn karma-niyamān anabhipretān api samaśikṣayad anuśiṣṭena hi bhāvyaṃ pituḥ putreṇeti //

4. With a heart deeply attached to his son through fatherly love, the Brahmin performed for him (such as he was) all the ceremonies up to Samavartana (the ceremony by which one gets discharged from pupilage in the Vedic school or Vedic study and from the estate of a bachelor) and, having performed his Upanayana

according to the rules, taught him how to keep himself clean, how to perform Achamana and other necessary courses of duties though they were not relished by the son; for (he thought) the son ought to be properly trained by the father.