अभिवादनशीलस्य नित्यं वृद्धोपसेविनः ।
चत्वारि तस्य वर्धन्ते आयुर्धर्मो यशो बलम् ॥ १२१ ॥He who habitually salutes and constantly pays reverence to the experienced obtains an increase in four (things), (viz.,) lifespan, virtue, fame, and strength. (Manusmriti 2.121)
A similar text is also found in the Buddhist literature. This sloka teaches one to respect the elderly and aged persons; longevity, merit, fame, and strength are rewarded in return.