SB 4.8.61

viraktaś cendriya-ratau
 bhakti-yogena bhūyasā
taṁ nirantara-bhāvena
 bhajetāddhā vimuktaye
Word for word: 
viraktaḥ ca — completely renounced order of life; indriya-ratau — in the matter of sense gratification; bhakti-yogena — by the process of devotional service; bhūyasā — with great seriousness; tam — unto Him (the Supreme); nirantara — constantly, twenty-four hours daily; bhāvena — in the topmost stage of ecstasy; bhajeta — must worship; addhā — directly; vimuktaye — for liberation.
Translation: 
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: 

There are different stages of perfection according to different persons’ objectives. Generally people are karmīs, for they engage in activities of sense gratification. Above the karmīs are the jñānīs, who are trying to become liberated from material entanglement. Yogīs 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 Mahārāja 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 mokṣa. 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 mokṣa, or liberation, is performed without any such desire. This is explained in the Bhakti-rasāmṛta-sindhu by the term anyābhilāṣitā-śūnyam, “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 kāma are meant for sense gratification, but when one comes to the stage of mokṣa, 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, Nārada Muni recommends that one directly engage himself in devotional service.