The wise versed in the Vedas declare life-span to be of three kinds — superior, middling, and inferior; it is expounded as piṇḍāyu, aṃśāyu, and dehāyu.
Piṇḍāyu applies when the Sun is strong, natural span when the Moon is strong, raśmi-born years for Mars, aṣṭavarga-refined span for Mercury, kālachakra-born life for Venus, daśāyu for Jupiter, samudāyu for Saturn; when the lagna is strongest the wise declare aṃśāyu.
Verse 3 — Who Is Entitled to Computed Longevity
आयुषोऽधिकारिणः । ये धर्ममार्गनिरता द्विजदेवभक्ता ये पव्यभोजनरता विजितेन्द्रियश्च । येमानवाद्वृतिसत्कुलशीलसीमास्तेषामिदं कथितमायुरुदारधीभिः ॥
ye dharmamārganiratā dvijadevabhaktā ye pavyabhojanaratā vijitendriyaśca | yemānavādvṛtisatkulaśīlasīmāsteṣām idaṃ kathitamāyur udāradhībhiḥ ||
Those devoted to the path of dharma, devoted to brahmins and gods, delighting in pure food and self-controlled; those humans of good conduct, noble lineage and virtuous bounds — for them alone have the great-minded sages declared this computation of life-span.
Verse 4 — Untimely Death for the Wicked
ये पापलुब्धाश्वोराश्च देवब्राह्मणनिन्दकाः । सर्वाशिनश्च ये तेषामकालमरणं नृणाम् ॥
ye pāpalubdhāśvorāśca devabrāhmaṇanindakāḥ | sarvāśinaśca ye teṣāmakālamaraṇaṃ nṛṇām ||
Those greedy of sin, slanderers of gods and brahmins, and devourers of all — for such men death comes before its appointed time.