Musannaf Ibn Abi Shaybah

Hazrat Umm Musa narrates that Hazrat Umm Salama (may Allah be pleased with her) said: I swear that Hazrat Ali (may Allah be pleased with him) was the closest to the Messenger of Allah (peace and blessings be upon him) among the people in terms of covenant. She says: We were visiting the Messenger of Allah (peace and blessings be upon him) on the day he passed away in the house of Hazrat Aisha (may Allah be pleased with her). The Messenger of Allah (peace and blessings be upon him) kept repeatedly asking every little while in the morning, "Has Ali (may Allah be pleased with him) come?" She says: I thought that the Prophet (peace and blessings be upon him) had sent him on some errand. Then, after a little while, he came, and we felt that the Prophet (peace and blessings be upon him) had some task with him, so we left the house and sat by the door. Among all of us, I was the closest to the door. The Prophet (peace and blessings be upon him) called Hazrat Ali (may Allah be pleased with him) towards himself and kept whispering to him. Then, on that very day, the Prophet (peace and blessings be upon him) passed away. Thus, he (Ali, may Allah be pleased with him) was the closest to the Prophet (peace and blessings be upon him) in terms of covenant.