SB 5.8.26

evam aghaṭamāna-manorathākula-hṛdayo mṛga-dārakābhāsena svārabdha-karmaṇā yogārambhaṇato vibhraṁśitaḥ sa yoga-tāpaso bhagavad-ārādhana-lakṣaṇāc ca katham itarathā jāty-antara eṇa-kuṇaka āsaṅgaḥ sākṣān niḥśreyasa-pratipakṣatayā prāk-parityakta-dustyaja-hṛdayābhijātasya tasyaivam antarāya-vihata-yogārambhaṇasya rājarṣer bharatasya tāvan mṛgārbhaka-poṣaṇa-pālana-prīṇana-lālanānuṣaṅgeṇāvigaṇayata ātmānam ahir ivākhu-bilaṁ duratikramaḥ kālaḥ karāla-rabhasa āpadyata.
Synonyms: 
evam — in that way; aghaṭamāna — impossible to be achieved; manaḥ-ratha — by desires, which are like mental chariots; ākula — aggrieved; hṛdayaḥ — whose heart; mṛga-dāraka-ābhāsena — resembling the son of a deer; sva-ārabdha-karmaṇā — by the bad results of his unseen fruitive actions; yoga-ārambhaṇataḥ — from the activities of yoga performances; vibhraṁśitaḥ — fallen down; saḥ — he (Mahārāja Bharata); yoga-tāpasaḥ — executing the activities of mystic yoga and austerities; bhagavat-ārādhana-lakṣaṇāt — from the activities of devotional service rendered to the Supreme Personality of Godhead; ca — and; katham — how; itarathā — else; jāti-antare — belonging to a different species of life; eṇa-kuṇake — to the body of a deer calf; āsaṅgaḥ — so much affectionate attachment; sākṣāt — directly; niḥśreyasa — to achieve the ultimate goal of life; pratipakṣatayā — with the quality of being an obstacle; prāk — who previously; parityakta — given up; dustyaja — although very difficult to give up; hṛdaya-abhijātasya — his sons, born of his own heart; tasya — of him; evam — thus; antarāya — by that obstacle; vihata — obstructed; yoga-ārambhaṇasya — whose path of executing the mystic yoga practices; rāja-ṛṣeḥ — of the great saintly King; bharatasya — of Mahārāja Bharata; tāvat — in that way; mṛga-arbhaka — the son of a deer; poṣaṇa — in maintaining; pālana — in protecting; prīṇana — in making happy; lālana — in fondling; anuṣaṅgeṇa — by constant absorption; avigaṇayataḥ — neglecting; ātmānam — his own soul; ahiḥ iva — like a serpent; ākhu-bilam — the hole of a mouse; duratikramaḥ — unsurpassable; kālaḥ — ultimate death; karāla — terrible; rabhasaḥ — having speed; āpadyata — arrived.
Translation: 
Śukadeva Gosvāmī continued: My dear King, in this way Bharata Mahārāja 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: 

As will be seen in later verses, Bharata Mahārāja, 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-saṁhitā (5.54) it is said, karmāṇi nirdahati kintu ca bhakti-bhājām: “For those engaged in devotional service, bhakti-bhajana, the results of past deeds are indemnified.” According to this, Bharata Mahārāja could not be punished for his past misdeeds. The conclusion must be that Mahārāja 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 Mahārāja 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 brāhmaṇa body in the next life. It is with this conviction that we declare in our Back to Godhead magazine that devotees like the gosvāmīs living in Vṛndāvana 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.