Srimad-Bhagavatam: Canto 10 - Chapter 1 - Verse 34

Sanskrit:

नाहमिज्याप्रजातिभ्यां तपसोपशमेन वा ।तुष्येयं सर्वभूतात्मा गुरुशुश्रूषया यथा ॥ ३४ ॥

ITRANS:

nāham ijyā-prajātibhyāṁtapasopaśamena vātuṣyeyaṁ sarva-bhūtātmāguru-śuśrūṣayā yathā

Translation:

I, the Soul of all beings, am not as satisfied by ritual worship, brahminical initiation, penances or self-discipline as I am by faithful service rendered to one’s spiritual master.

Purport:

The word prajāti here indicates either begetting good children or the second birth obtained by ritual initiation into Vedic culture. Although both of these are praiseworthy, Lord Kṛṣṇa here states that faithful service rendered to a bona fide spiritual master is still higher.