Manava Dharmashastra 2.121

2.121

sarvāneva prati pūrvābhibhāṣitā yathārhā'bhivādanaśīlatā na punarabhivādanaśabdoccāraṇameva | śīlaśabdena prayojanāpekṣābhāva ucyate | nityaṃ vṛddhānupasevate priyavacanādinā, yathāśaktyā hyupakāreṇa cārādhayate | tasya catvāri sampravardhante | āyurdharmo'mutra svargādiphalapādapaḥ | yaśobale ca prāgukte | arthavādo'pyayaṃ phalāvagamahetuḥ |

For one who is in the habit of saluting and constantly revering elders,—four things prosper: viz., longevity, merit, fame and strength.—(121)

Medhātithi’s commentary (manubhāṣya):
The ‘habit of saluting’ stands, not only for the uttering of words of salute, but for the act of addressing all men with respect and in the proper manner. The term ‘habit’ indicates that the man does it without any personal motive at all.

‘Constantly reveres elders’—by talking agreeably, and also attends upon them with such service as he can render.

‘For him four things prosper—longevity, merit’—which is the tree that hears fruit in the other world, in the shape of Heaven,—‘fame and strength’—as described above.

Though this verse is purely valedictory, yet it serves to afford some idea as to the effects that ensue.—(121)

This verse is quoted in Vīramitrodaya, (Saṃskāra, p. 460);—in Vidhānapārijāta (p. 501) as describing the reward for saluting one’s superiors;—in Parāśaramādhava (Ācāra, p. 306) as eulogising the act of saluting one’s superiors;—and in Smṛticandrikā (Saṃskāra, p. 97).

Comparative notes by various authors
Āpastamba-Dharmasūtra (1.5.15).—‘Desiring Heaven and Longevity (one should salute the Teacher).’

Baudhāyana-Dharmasūtra (1.2.26).—‘Desiring Heaven and Longevity, one should grasp his right foot with the right hand and the left foot with the left.’