SB 9.4.67
mat-sevaya pratitam te
salokyadi-catustayam
necchanti sevaya purnah
kuto ’nyat kala-viplutam
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
My devotees, who are always satisfied to be engaged in My loving service, are not interested even in the four principles of liberation [salokya, sarupya, samipya and sarsti], although these are automatically achieved by their service. What then is to be said of such perishable happiness as elevation to the higher planetary systems?
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Srila Bilvamangala Thakura has estimated the value of liberation as follows:
muktih svayam mukulitañjalih sevate ’sman
dharmartha-kama-gatayah samaya-pratiksah
Bilvamangala Thakura realized that if one develops his natural devotional service to the Supreme Personality of Godhead, mukti stands before him with folded hands to offer all kinds of service. In other words, the devotee is already liberated. There is no need for him to aspire for different types of liberation. The pure devotee automatically achieves liberation, even without desiring it.