Bhagavad Gita · Jnana Karma Sannyasa YogaChapter 4, Shloka 39 (4.39)

Three conditions — one sequence.

1. Śraddhā — faith.
2. Tat-para — Shankaracharya: śraddhālutve 'pi bhavati kaścin manda-prasthānaḥ — even with faith, someone may be slack; hence tat-paraḥ guru-upāsadanādau abhiyuktaḥ — devoted to going to the guru and the like.
3. Saṃyatendriya — tat-paro 'pi ajitendriyaḥ syāt — even one who is devoted may not have conquered the senses; hence restraint.

Shankaracharya — outer and inner means. An important point: praṇipātādis tu bāhyo 'naikāntiko 'pi bhavati māyāvitvādi-sambhavāt, na tu tat śraddhāvattvādau — prostration and the like are outward and also uncertain, because pretence (māyāvitva) is possible in them; but not in faith, devotion and restraint — so these are ekāntataḥ jñāna-labdhy-upāyaḥ — sure means of gaining knowledge. The result: jñānaṃ labdhvā parāṃ mokṣākhyāṃ śāntim … acireṇa kṣipram eva — supreme peace, called liberation, quickly.

Acharya Ramanuja: having gained knowledge through teaching, one who has faith in the growth of that knowledge, whose mind is set on it alone, and who holds the senses back from other objects, acireṇa kālena ukta-lakṣaṇa-vipāka-daśāpannaṃ jñānaṃ labhate — soon gains ripened knowledge; and through it paraṃ nirvāṇaṃ prāpnoti — attains supreme nirvana.