Musnad Abi Ya'la 592 — he stated: I had an appointed time before dawn

It is narrated from Sayyiduna Ali bin Abi Talib (may Allah be pleased with him) that he stated: "I had an appointed time before dawn (sahar) with the Messenger of Allah (peace and blessings be upon him), in which I would come to him (peace and blessings be upon him). When I came, I would ask permission; if I found him (peace and blessings be upon him) praying, he (peace and blessings be upon him) would say the tasbih 'Subhan Allah' (Allah is free of all imperfection) and I would enter, and if I found him (peace and blessings be upon him) free, he would give me permission. One night I came to him (peace and blessings be upon him), and he (peace and blessings be upon him) gave me permission and said: 'The angel came to me', or he said: 'Jibril (peace be upon him) came to me', 'and I said (requesting): "Come in." But he replied: "There is something in the house because of which I cannot enter." I looked and said: "I do not see anything." Then I searched, and he said to me: "Look." I looked carefully and found a puppy belonging to Sayyiduna al-Husayn bin Ali (may Allah be pleased with them both) tied to the leg of the bed in the house of Sayyidah Umm Salamah (may Allah be pleased with her). Then he (Jibril) said: "Indeed the angels", or he said: "We, the company of angels, do not enter a house in which there is an image, a dog or a person in a state of major ritual impurity (one on whom ghusl is obligatory)."'"