Need one be absolutely sure about a guru to become his disciple?
You can never be absolutely sure about a guru, and that is not needed. What is needed is that you should be absolutely sure about yourself. How can you be sure about a master? You exist on two different levels, two different states of mind. Whatsoever you can see, whatsoever you can understand, whatsoever you can interpret, will not be of much use – and there is more possibility of your going wrong than right. But there is no need, so don’t be worried about it…
Vedanta: Seven Steps To Samadhi:The Akshya Upanishad
In Deep Patience