After considering his advanced age and deliberating on the welfare of his spiritual self, King Uttānapāda detached himself from worldly affairs and entered the forest.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
आत्मानं च प्रवयसमाकलय्य विशाम्पतिः । वनं विरक्तः प्रातिष्ठद्विमृशन्नात्मनो गतिम्
ātmānaṃ ca pravayasamākalayya viśāmpatiḥ | vanaṃ viraktaḥ prātiṣṭhadvimṛśannātmano gatim
SB 4.9.67