Bhagavatapurana 1.19.7

1.19.7

iti vyavacchidya sa pāṇḍaveyaḥ prāyopaveśaṃ prati viṣṇupadyām /
dadhau mukundāṅghrim ananyabhāvo munivrato muktasamastasaṅgaḥ //

7. That descendant of the Pandavas reflected thus and decided on the vow of fasting (to be kept) on (the banks of) the river flowing from Vishnu's feet; and, having no other thought he contemplated the feet of *Mukunda*, observing the austerities of a hermit and free from all attachments.