Musannaf Ibn Abi Shaybah

Hazrat Abdullah bin Naji narrates that Hazrat Ali (may Allah be pleased with him) said: I used to go to the Noble Prophet (peace and blessings be upon him) twice; once during the day and once at night. So whenever I would come to the Prophet (peace and blessings be upon him) and he would be offering prayer, he (peace and blessings be upon him) would clear his throat for me.