Manava Dharmashastra 2.228

2.228

tasmāttayormātāpitrorācāryasya ca sarvadā yāvajjīvaṃ yatpriyaṃ teṣāṃ tatkuryāt, na sakṛd dvikhirvā kṛtvā kṛtī bhavet | teṣvevācāryādiṣu triṣu tuṣṭeṣu bhaktyārādhiteṣu tapaḥ sarvaṃ bahvanvarṣagaṇāṃścāndrāyaṇādi tapastaptvā yatphala prāptyate tattatparitoṣādeva labhyata iti |

He should always do what is pleasing to those two and to the preceptor; on these three being satisfied, all austerity becomes completed.—(228)

Medhātithi’s commentary (manubhāṣya):
For reasons stated above,—‘of these two’—of the father and the mother,—‘and of the preceptor,’—‘always’—as long as one lives,—‘he should do what is pleasing to’; and one should not be satisfied with acting agreeably to them once, twice or thrice only.

‘On these three’—preceptor and the rest—‘being satisfied’—i.e., when they have been propitiated by devoted service,—‘all austerity’; i.e., the rewards that Are obtained by the performance of the ‘Cāndrāyaṇa’ and other penances for several years are obtained from the satisfaction of these three.—(228)