Srimad Bhagavatam Canto 07, Chapter 10, Text 40

SB 7.10.40

yatha yatha bhagavato
 bhaktya paramayabhida
nrpas caidyadayah satmyam
 hares tac-cintaya yayuh
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
By devotional service, pure devotees who incessantly think of the Supreme Personality of Godhead receive bodies similar to His. This is known as sarupya-mukti. Although Sisupala, Dantavakra and other kings thought of Krsna as an enemy, they also achieved the same result.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
In Caitanya-caritamrta, in connection with Lord Caitanya’s instructions to Sanatana Gosvami, it is explained that a devotee should externally execute his routine devotional service in a regular way but should always inwardly think of the particular mellow in which he is attracted to the service of the Lord. This constant thought of the Lord makes the devotee eligible to return home, back to Godhead. As stated in Bhagavad-gita (4.9), tyaktva deham punar janma naiti mam eti: after giving up his body, a devotee does not again receive a material body, but goes back to Godhead and receives a spiritual body resembling those of the Lord’s eternal associates whose activities he followed. However the devotee likes to serve the Lord, he may constantly think of the Lord’s associates — the cowherd boys, the gopis, the Lord’s father and mother, His servants and the trees, land, animals, plants and water in the Lord’s abode. Because of constantly thinking of these features, one acquires a transcendental position. Kings like Sisupala, Dantavakra, Kamsa, Paundraka, Narakasura and Salva were all similarly delivered. This is confirmed by Madhvacarya:
paundrake narake caiva
 salve kamse ca rukmini
avistas tu harer bhaktas
 tad-bhaktya harim apire
Paundraka, Narakasura, Salva and Kamsa were all inimical toward the Supreme Personality of Godhead, but because all these kings constantly thought of Him, they achieved the same liberation — sarupya-mukti. The jñana-bhakta, the devotee who follows the path of jñana, also attains the same destination. If even the enemies of the Lord achieve salvation by constantly thinking about the Lord, what is to be said of pure devotees who always engage in the Lord’s service and who think of nothing but the Lord in every activity?
Srimad Bhagavatam Canto 07, Chapter 10, Text 39
Srimad Bhagavatam Canto 07, Chapter 10, Text 41