Tridandiswami Sri Srimad Bhaktivedanta Narayana Maharaja extols the glories of Guru Tattva:
A guru who can fall down so many times is actually not a guru. In order for one to be guru, so many qualifications must be in him. If he has the false ego that, “I am guru,” remembering some slokas and teachings but in his heart he has so many worldly desires, so much lust – but he has covered everything in his heart – then he is not qualified. He may have taken sannyasa, the renounced order, but he is fallen. Third class persons don’t realize that their guru is fallen. Srila Bhaktivedanta Svami Maharaja gave some scope even to those who were fallen from the beginning. He told them, “You should preach and become a very high class devotee,” but they fell down.
In order to be guru, one must be in the stage of madhyama-madhyama or madhyama-uttama. He must be realizing something, knowing the Vedas, Upanisads and all sastra, and he must be able to wash away all kinds of doubts forever. He will have realization of the beauty and sweetness of Krsna and Radhika, he will know what is bhakti and what is prema, and he will be detached from all kinds of worldly, bogus things. Then he is guru.
If he does not have these qualities, then he is not qualified to make any disciple. He is not allowed to do so. It may be that someone unknowingly accepted an unqualified guru. It may be that at first he was not qualified to recognize a good guru and someone told him to take initiation, so he did so. Then, after some time he may think, “He cannot help me to be a good devotee.” In such circumstance we should give up that unqualified guru and take a new guru.
That person cannot help us because he cannot help himself. It is like a blind person trying to help another blind person to reach any goal, but there was a pit and both people fell in. How can a blind person help another blind person to find their destination? It is absurd.
The devotee must have a high caliber of guru. He can help.
Source : home program in Heidelberg, Germany