Srimad Bhagavatam Canto 04, Chapter 08, Text 61

SB 4.8.61

viraktas cendriya-ratau
bhakti-yogena bhuyasa
tam nirantara-bhavena
bhajetaddha vimuktaye
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
If one is very serious about liberation, he must stick to the process of transcendental loving service, engaging twenty-four hours a day in the highest stage of ecstasy, and he must certainly be aloof from all activities of sense gratification.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
There are different stages of perfection according to different persons’ objectives. Generally people are karmis, for they engage in activities of sense gratification. Above the karmis are the jñanis, who are trying to become liberated from material entanglement. Yogis are still more advanced because they meditate on the lotus feet of the Supreme Personality of Godhead. And above all these are the devotees, who simply engage in the transcendental loving service of the Lord; they are situated seriously on the topmost platform of ecstasy.
Here Dhruva Maharaja is advised that if he has no desire for sense gratification, then he should directly engage himself in the transcendental loving service of the Lord. The path of apavarga, or liberation, begins from the stage called moksa. In this verse the word vimuktaye, “for liberation,” is especially mentioned. If one wants to be happy within this material world, he may aspire to go to the different material planetary systems where there is a higher standard of sense gratification, but real moksa, or liberation, is performed without any such desire. This is explained in the Bhakti-rasamrta-sindhu by the term anyabhilasita-sunyam, “without desire for material sense gratification.” For persons who are still inclined to enjoy material life in different stages or on different planets, the stage of liberation in bhakti-yoga is not recommended. Only persons who are completely free from the contamination of sense gratification can execute bhakti-yoga, or the process of devotional service, very purely. The activities on the path of apavarga up to the stages of dharma, artha and kama are meant for sense gratification, but when one comes to the stage of moksa, the impersonalist liberation, the practitioner wants to merge into the existence of the Supreme. But that is also sense gratification. When one goes above the stage of liberation, however, he at once becomes one of the associates of the Lord to render transcendental loving service. That is technically called vimukti. For this specific vimukti liberation, Narada Muni recommends that one directly engage himself in devotional service.
Srimad Bhagavatam Canto 04, Chapter 08, Text 59-60
Srimad Bhagavatam Canto 04, Chapter 08, Text 62