Musannaf Ibn Abi Shaybah 27334 — Asking permission

Abdullah bin Nujayy said that Sayyiduna Ali (may Allah be pleased with him) said: I used to go to the Prophet (peace and blessings be upon him) twice, once during the day and once at night. When I came to him (peace and blessings be upon him) while he (peace and blessings be upon him) was praying, he (peace and blessings be upon him) would clear his throat for me.