Narrated Salma:
"I entered upon Umm Salamah while she was crying, so I said: 'What causes you to cry?' She said: 'I saw the Messenger of Allah - that is, in a dream - and there was was dirt on his head and his beard. so I said: "What is wrong with you, O Messenger of Allah?" He said: 'I just witnessed the killing of Al-Husain.'"
English reference: Vol. 1, Book 46, Hadith 3771
Arabic reference: Book 49, Hadith 4140