The Compendium of Caraka 5.1.7_3

5.1.7_3

nimittānurūpā tu nimittārthānukāriṇī yā, tāmanimittāṃ nimittamāyuṣaḥ pramāṇajñānasyecchanti bhiṣajo bhūyaścāyuṣaḥ kṣayanimittāṃ pretaliṅgānurūpāṃ, yāmāyuṣo+&antargatasya jñānārthamupadiśanti dhīrāḥ/

That which corresponds to a cause is that which imitates the object of a cause; physicians consider this causeless [alteration] to be a sign for knowing the remaining span of life, and furthermore, being caused by the exhaustion of life, it corresponds to the signs of death, which the wise teach for the sake of knowing the term of life.