Vaishnava Dharmashastra 30.47

30.47

ya āvṛṇoty avitathena karṇāv aduḥkhaṃ kurvann amṛtaṃ saṃprayacchan
taṃ manyeta pitaraṃ mātaraṃ ca tasmai na druhyet kṛtam asya jānan //

He who fills his ears with holy truths, who frees him from all pain (in this world and the next). and confers immortality (or final liberation) upon him, that man let the student consider as his (true) father and mother: gratefully acknowledging the debt he owes him, he must never grieve him.