Imam Malik's Muwatta, Chapter: Burials

Malik related to me from AIqama ibn Abi Alqama that his mother said that she had heard A'isha, the wife of the Prophet, may Allah bless him and grant him peace, say, "The Messenger of Allah, may Allah bless him and grant him peace, rose one night and put on his clothes and then went out. I ordered my slave-girl, Barira, to follow him, and she followed him until he got to al-Baqi. He stood near it as long as Allah willed and then he left. Barira arrived back before him and told me and I did not say anything to him until morning, and then I mentioned it to him and he explained, 'I was sent out to the people of al-Baqi to pray for them.' "