Aadi Guru:
The first guru.
Chitram Vatatarormula Vriddhaa: Sishyaa: Gururyuva
Gurostu maunam Vyakhyanam Sishyaastu Chinna Samsaya:
It is a surprise to see the young Guru Dakshinamurty sitting at the vata Vriksh teaching older desciples( the Sapta Rishis ) through silence and making them free from doubts.
It is said that Shiva imparted knowledge on Guru Purnima first time to Seven Sages through silence and they understood the real essence of the knowledge. Their doubts clarified,they bowed before Sree Dakshina Murty
Tasmai Sri Guru murtaye Nama idam Sri Dakshinamurtaye.
Adi Sankara described thus and I bow before Shiv Sankar and Sankaracharya for bestowing and spreading knowledge.