It is narrated from Sayyiduna Buraydah (may Allah be pleased with him) that he said: I set out with Abu Dharr and his cousin Nu'aym in search of the Messenger of Allah (peace and blessings be upon him), who at that time was hidden in a mountain. Abu Dharr (may Allah be pleased with him) said: O Muhammad (peace and blessings be upon him)! We have come to you to hear what you say and to learn what you call to. The Messenger of Allah (peace and blessings be upon him) said: "I bear witness that there is no god but Allah and that I am the Messenger of Allah." So Abu Dharr and his companion believed, and I too believed. At that time Sayyiduna Ali (may Allah be pleased with him) had gone out on some errand for the Messenger of Allah (peace and blessings be upon him). Revelation came down upon the Messenger of Allah (peace and blessings be upon him) on Monday, and Sayyiduna Ali (may Allah be pleased with him) prayed on Tuesday. The chain of this hadith is sahih (authentic), but the two Shaykhs did not record it.