This verse is spoken by Prahlāda Mahārāja in Śrīmad-Bhāgavatam (7.9.10). A brāhmaṇa is supposed to be qualified with twelve qualities. As stated in the Mahābhārata:

dharmaś ca satyaṁ ca damas tapaś ca
 amātsaryaṁ hrīs titikṣānasūyā
yajñaś ca dānaṁ ca dhṛtiḥ śrutaṁ ca
 vratāni vai dvādaśa brāhmaṇasya

“A brāhmaṇa must be perfectly religious. He must be truthful, and he must be able to control his senses. He must execute severe austerities, and he must be detached, humble and tolerant. He must not envy anyone, and he must be expert in performing sacrifices and giving whatever he has in charity. He must be fixed in devotional service and expert in the knowledge of the Vedas. These are the twelve qualifications for a brāhmaṇa.”

The Bhagavad-gītā (18.42) describes the brahminical qualities in this way:

śamo damas tapaḥ śaucaṁ kṣāntir ārjavam eva ca
jñānaṁ vijñānam āstikyaṁ brahma-karma svabhāva-jam

“Peacefulness, self-control, austerity, purity, tolerance, honesty, knowledge, wisdom and religiousness — these are the natural qualities by which the brāhmaṇas work.”

In the Muktāphala-ṭīkā, it is said:

śamo damas tapaḥ śaucaṁ kṣānty-ārjava-viraktayaḥ
jñāna-vijñāna-santoṣāḥ satyāstikye dvi-ṣaḍ guṇāḥ

“Mental equilibrium, sense control, austerity, cleanliness, tolerance, simplicity, detachment, theoretical and practical knowledge, satisfaction, truthfulness and firm faith in the Vedas are the twelve qualities of a brāhmaṇa.”