Srimad Bhagavatam Canto 05, Chapter 08, Text 26

SB 5.8.26

evam aghatamana-manorathakula-hrdayo mrga-darakabhasena svarabdha-karmana yogarambhanato vibhramsitah sa yoga-tapaso bhagavad-aradhana-laksanac ca katham itaratha jaty-antara ena-kunaka asangah saksan nihsreyasa-pratipaksataya prak-parityakta-dustyaja-hrdayabhijatasya tasyaivam antaraya-vihata-yogarambhanasya rajarser bharatasya tavan mrgarbhaka-posana-palana-prinana-lalananusangenaviganayata atmanam ahir ivakhu-bilam duratikramah kalah karala-rabhasa apadyata.
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
Sukadeva Gosvami continued: My dear King, in this way Bharata Maharaja was overwhelmed by an uncontrollable desire which was manifest in the form of the deer. Due to the fruitive results of his past deeds, he fell down from mystic yoga, austerity and worship of the Supreme Personality of Godhead. If it were not due to his past fruitive activity, how could he have been attracted to the deer after giving up the association of his own son and family, considering them stumbling blocks on the path of spiritual life? How could he show such uncontrollable affection for a deer? This was definitely due to his past karma. The King was so engrossed in petting and maintaining the deer that he fell down from his spiritual activities. In due course of time, insurmountable death, which is compared to a venomous snake that enters the hole created by a mouse, situated itself before him.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
As will be seen in later verses, Bharata Maharaja, at the time of death, would be forced to accept the body of a deer due to his attraction for the deer. In this regard, a question may be raised. How can a devotee be affected by his past misconduct and vicious activities? In Brahma-samhita (5.54) it is said, karmani nirdahati kintu ca bhakti-bhajam: “For those engaged in devotional service, bhakti-bhajana, the results of past deeds are indemnified.” According to this, Bharata Maharaja could not be punished for his past misdeeds. The conclusion must be that Maharaja Bharata purposefully became over-addicted to the deer and neglected his spiritual advancement. To immediately rectify his mistake, for a short time he was awarded the body of a deer. This was just to increase his desire for mature devotional service. Although Bharata Maharaja was awarded the body of an animal, he did not forget what had previously happened due to his purposeful mistake. He was very anxious to get out of his deer body, and this indicates that his affection for devotional service was intensified, so much so that he was quickly to attain perfection in a brahmana body in the next life. It is with this conviction that we declare in our Back to Godhead magazine that devotees like the gosvamis living in Vrndavana who purposely commit some sinful activity are born in the bodies of dogs, monkeys and tortoises in that holy land. Thus they take on these lower life forms for a short while, and after they give up those animal bodies they are again promoted to the spiritual world. Such punishment is only for a short period, and it is not due to past karma. It may appear to be due to past karma, but it is offered to rectify the devotee and bring him to pure devotional service.
Srimad Bhagavatam Canto 05, Chapter 08, Text 25
Srimad Bhagavatam Canto 05, Chapter 08, Text 27