الكافي 1/2/6/1

1. Ali ibn Muhammad ibn ‘Abdallah has narrated from Ahmad ibn Muhammad from Muhammad ibn Khalid from Sulayman ibn Ja’far al-Ja’fari from a person he mentioned from Abu ‘Abdillah (al-Sadiq) عليه السلام that Amir al-Mu'minin عليه السلام used to say, "Among the rights of a scholar is that one must not overburden him with many questions nor should one pull on his garment (question excessively). When one would enter in his presence while other people are there one should offer general salutation to all of them and a special greeting directed towards the scholar only. One must sit before him and not behind him. One must not wink with his eyes nor make signal with one's hands and one must not excessively cite others by saying, "So-and-so said this" and "So-and-so said that" in contradiction to his words. One must not become impatient with the length of his companionship. For the scholar is like a date palm-you must wait patiently until something falls from it for you. And the scholar has a greater reward than one who fasts, prays, and fights in the way of Allah."