Śrīmad-Bhāgavatam · Text 5.12.14
Who is speaking and story frame
अहं पुरा भरतो नाम राजा
विमुक्तदृष्टश्रुतसङ्गबन्ध: ।
आराधनं भगवत ईहमानो
मृगोऽभवं मृगसङ्गाद्धतार्थ: ॥ १४ ॥
ahaṁ purā bharato nāma rājā
vimukta-dṛṣṭa-śruta-saṅga-bandhaḥ
ārādhanaṁ bhagavata īhamāno
mṛgo ’bhavaṁ mṛga-saṅgād dhatārthaḥ
In a previous birth I was known as Mahārāja Bharata. I attained perfection by becoming completely detached from material activities through direct experience, and through indirect experience I received understanding from the Vedas. I was fully engaged in the service of the Lord, but due to my misfortune, I became very affectionate to a small deer, so much so that I neglected my spiritual duties. Due to my deep affection for the deer, in my next life I had to accept the body of a deer.
Read Śrīla Prabhupāda's purport on Vedabase.io