According to tradition Adi Shankaracharya was a great teacher of Advaita Vedanta. Once he was going to bathe in the Ganga in Kashi.
On the way he met a man walking with his dogs. Shankaracharya’s disciples asked him to move out of the way.
The man asked calmly, “Whom are you asking to move, this body or the Self within? A body made of food is no different from another body made of food, and the Self is one in all.”
Folk tradition says Shankaracharya was moved by this reply. He bowed to the man, and in this spirit composed the Manisha Panchakam, which says that whoever has this knowledge of non-duality is my guru.