“You should understand who is a real guru. He is the abode of bhakti, and he has all kinds of serving moods towards Radha-Krishna Conjugal or Mahaprabhu. He can give sadhana-bhakti, and he can also give rati - a high class of rati. If he is qualified to even give prema-bhakti in Goloka Vrindavana, and the love and affection of Conjugal Radha-Krishna, can he fall down? Never. How much qualified must that guru be, that he can take all ignorant persons to Krishna? If he himself is falling down, then he is actually not guru. You are intelligent enough to reconcile all these things, and to understand who is the real guru.”

Śrila Gurudeva Bhaktivedānta Nārāyaṇa Gosvāmī Mahārāja
Guru Tattva: Real And Apparent, Moscow July 30, 2000