So guru must be a brāhmaṇa, mean a qualified brāhmaṇa, not born-brāhmaṇa, so-called brāhmaṇa. Qualified brāhmaṇa. So still, brāhmaṇa's qualification, ṣaṭ-karma, paṭhana pāṭhana yajana yājana dāna pratigraha. So śāstra says that ṣaṭ-karma-nipuṇo vipraḥ. If one vipra is quite expert in executing the six kinds of business, and mantra-tantra-viśāradaḥ, and very well known in the Vedic mantras and hymns and everything complete, but if he is avaiṣṇava, if he is not Vaiṣṇava, he does not know viṣṇu-tattva, or kṛṣṇa-tattva, then he cannot become spiritual master. Avaiṣṇavo gurur na syād vaiṣṇavaḥ śva-paco guruḥ. But if a Vaiṣṇava, one who knows viṣṇu-tattva, kṛṣṇa-tattva, even if he's born in the family of śva-paca, the dog-eaters, caṇḍāla, he can be accepted as guru. So the real test is whether the guru is a Vaiṣṇava, whether he know the science of Kṛṣṇa. That is also confirmed by Caitanya Mahāprabhu:
- kibā vipra, kibā nyāsī, śūdra kene naya
- yei kṛṣṇa-tattva-vettā sei 'guru' haya
- (CC Madhya 8.128)
A... It doesn't matter what he is, whether he's a sannyāsī or a gṛhastha or a brāhmaṇa or a su..., born in brāhmaṇa family or... It doesn't matter. Yei kṛṣṇa-tattva. Anyone who knows Kṛṣṇa, he can become guru, not others. So that is the statement of the śāstras. Avaiṣṇava cannot become guru.