A guru, or spiritual master, can be anyone who is well conversant with the science of Krsna

Expressions researched:
"A guru, or spiritual master, can be anyone who is well conversant with the science of Krsna"

SB Canto 7

A guru, or spiritual master, can be anyone who is well conversant with the science of Kṛṣṇa. Therefore although Prahlāda Mahārāja was a gṛhastha ruling over the demons, he was a paramahaṁsa, the best of human beings, and thus he is our guru. In the list of gurus, or authorities, Prahlāda Mahārāja's name is therefore mentioned.

SB 7.13.46, Translation and Purport:

Nārada Muni continued: After Prahlāda Mahārāja, the King of the demons, heard these instructions from the saint, he understood the occupational duties of a perfect person (paramahaṁsa). Thus he duly worshiped the saint, took his permission and then left for his own home.

As quoted in Caitanya-caritāmṛta (CC Madhya 8.128), Śrī Caitanya Mahāprabhu said:

kibā vipra, kibā nyāsī, śūdra kene naya

yei kṛṣṇa-tattva-vettā sei 'guru' haya

A guru, or spiritual master, can be anyone who is well conversant with the science of Kṛṣṇa. Therefore although Prahlāda Mahārāja was a gṛhastha ruling over the demons, he was a paramahaṁsa, the best of human beings, and thus he is our guru. In the list of gurus, or authorities, Prahlāda Mahārāja's name is therefore mentioned:

svayambhūr nāradaḥ śambhuḥ

kumāraḥ kapilo manuḥ

prahlādo janako bhīṣmo

balir vaiyāsakir vayam

The conclusion is that a paramahaṁsa is an exalted devotee (bhagavat-priya). Such a paramahaṁsa may be in any stage of life—brahmacāri, gṛhastha, vānaprastha or sannyāsa—and be equally liberated and exalted.