प्रस्थिते तु वनं पित्रा दत्त्वा गां धर्मसंश्रयः षट्त्रिंशद्वर्षसाहस्रं रक्षिताव्याहतेन्द्रियः
prasthite tu vanaṁ pitrā dattvā gāṁ dharma-saṁśrayaḥ ṣaṭ-triṁśad-varṣa-sāhasraṁ rakṣitāvyāhatendriyaḥ
Synonyms
prasthite—after departure; tu—but; vanam—to the forest; pitrā—by your father; dattvā—awarding; gām—the whole world; dharma-saṁśrayaḥ—under the protection of piety; ṣaṭ-triṁśat—thirty-six; varṣa—years; sāhasram—one thousand; rakṣitā—you will rule; avyāhata—without decay; indriyaḥ—the power of the senses..
Translation
After your father goes to the forest and awards you the rule of his kingdom, you will rule the entire world continuously for 36,000 years, and all your senses will continue to be as strong as they are now. You will never become old.
Purport
In the Satya-yuga people generally lived for 100,000 years. Dhruva Mahārāja's ruling the world for 36,000 years was quite possible in those days.