The Compendium of Caraka 3.3.38

3.3.38

tamuvāca bhagavānātreyaḥ---śrūyatāmagniveśa! yathā yānasamāyukto 'akṣaḥ prakṛtyaivākṣaguṇairupetaḥ sa ca sarvaguṇopapanno vāhyamāno yathākālaṃ svapramāṇakṣayādevāvasānaṃ gacchet, tathā++āyuḥ śarīropagataṃ balavatprakṛtyā yathāvadupacaryamāṇaṃ svapramāṇakṣayādevāvasānaṃ gacchati; sa mṛtyuḥ kāle/

The venerable Ātreya said to him: "Listen, Agniveśa! Just as an axle fitted to a vehicle, endowed by its very nature with the qualities of an axle and furnished with every excellence, when driven, will reach its end in due time solely through the depletion of its own span; so also a lifespan associated with the body, strong by nature and properly cared for, reaches its end solely through the depletion of its own measure. That is death in due time.