Manava Dharmashastra 2.120

2.120

pūrvasyārthavādaḥ | sthavire vṛddhavayasyāyatyāgacchati, yūnastaruṇasyordhvaṃ prāṇāḥ jīvitahetavo'ntarmaruta ūrdhvamāsyādbahirniṣkrāmanti | apānavṛttiṃ parityajya jīvavicchedaṃ cikīrṣanti | pratyutthāya yadabhivādanaṃ kriyate tena yathāpūrvaṃ jīvitasthemne kalpante | pratipadyate pratyujjīvati |

On the elder approaching, the vital breaths of the younger rush outward; and he recovers them by the acts of rising to meet and salute him.—(120)

Medhātithi’s commentary (manubhāṣya):
This verse is commendatory to what has gone before.

‘On the elder’—the person of higher age—‘approaching’—coming up,—‘the vital breaths’—the sources of life, the inner airs—‘of the younger’—‘rush outward’—move out; i.e., giving up their functions, they intend to cut off his life.

When however he rises to meek him and salutes him, the breaths proceed, as before, to sustain his life.

‘Recovers’—becomes resuscitated.—(120)

This verse is quoted in Vīramitrodaya (Saṃskāra, p. 460);—again in the same work (Ācāra, p. 150), where ‘Āyāti’ is explained as ‘āyocchati’;—and in Smṛticandrikā (Saṃskāra, p. 97), as laying down that before saluting one should rise.

Comparative notes by various authors
Vaśiṣṭha-smṛti (13.13).—‘The Priest, the Father-in-law, the paternal uncle, the maternal uncle—those not junior in age;—these he shall salute after standing to receive them.’ Āpastamba, (Parāśaramādhava, p. 297)—[reproduces Manu].

Mahābhārata (13.104.64-65).—(same as Manu).