Ashad Purnima, dedicated to the Guru, celebrates the master-disciple relationship of highest love on the earth. All religions observe this relationship in their unique way. 
Osho talks about Sufis who have an interesting story highlighting this relationship. Sufi Master Junnaid, a seeker, used to tell his disciples, “When I met my master, he never looked at me for three years. But I was persistent. I stayed there right in front of him.” 

After three years the master looked at him for the first time. That was the recognition that he was not a student, but a disciple. A student would have got lost in three years; no student can stay that long waiting just for a look. Then another three years passed and he never looked again. 

After three years the master looked again and smiled. His smile cut through the heart of Junnaid, who wondered why he had smiled. But the master did not give him a chance to ask. He started talking to other disciples. After another three years, he called him and kissed his forehead. “My son, now you are ready. Now you can go and spread the message.” 

But he hadn't been given any message. He couldn't figure out what the message could be. But if the master was urging him to go, he would have to. So, touching his master's feet, Junnaid left for his mission. 

A master kissing the devotee is a declaration that the merger (between the master and disciple) has taken place. Osho explains that a spiritual seeker passes through three stages in life — student, disciple and devotee. The student is unconscious. The disciple starts becoming conscious. The devotee is so conscious that he cannot be conscious of his consciousness. 

It has to be a recognition from the master because from the devotee the distance between himself and the master is nil. From the devotee one grows into a master, but it is a spontaneous and natural growth.