Srimad-Bhagavatam: Canto 11 - Chapter 1 - Verse 30


भक्तिं लब्धवत: साधो: किमन्यदवशिष्यते ।मय्यनन्तगुणे ब्रह्मण्यानन्दानुभवात्मनि ॥ ३० ॥


bhaktiṁ labdhavataḥ sādhoḥkim anyad avaśiṣyatemayy ananta-guṇe brahmaṇyānandānubhavātmani


What more remains to be accomplished for the perfect devotee after achieving devotional service unto Me, the Supreme Absolute Truth, whose qualities are innumerable and who am the embodiment of all ecstatic experience?


Devotional service to Lord Kṛṣṇa is so pleasing that a pure devotee cannot desire anything except service to the Lord. In the Tenth Canto of Śrīmad-Bhāgavatam, Lord Kṛṣṇa told the gopīs that they would have to accept their own service as the ultimate reward of their devotion to Him, since nothing awards as much happiness and knowledge as devotional service itself. When one sincerely chants and hears the holy name and fame of Lord Kṛṣṇa, the heart is purified and gradually one can appreciate the actual, blissful nature of Kṛṣṇa consciousness, loving service to the Lord.