Bhagavatapurana 4.9.22

4.9.22

prasthite tu vanaṃ pitrā dattvā gāṃ dharma-saṃśrayaḥ /
ṣaṭ-triṃśad-varṣa-sāhasraṃ rakṣitāvyāhatendriyaḥ //

22. When thy father makes over the earth to thee and retires to the forest, thou shalt firm in righteousness and endowed with unimpaired senses (faculties), be the protector of the world for thirty-six thousand years.