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 (ﷺ) - 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.'"
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا أَبُو سَعِيدٍ الأَشَجُّ، قَالَ حَدَّثَنَا أَبُو خَالِدٍ الأَحْمَرُ، قَالَ حَدَّثَنَا رَزِينٌ، قَالَ حَدَّثَتْنِي سَلْمَى، قَالَتْ دَخَلْتُ عَلَى أُمِّ سَلَمَةَ وَهِيَ تَبْكِي فَقُلْتُ مَا يُبْكِيكِ قَالَتْ رَأَيْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم - تَعْنِي فِي الْمَنَامِ - وَعَلَى رَأْسِهِ وَلِحْيَتِهِ التُّرَابُ فَقُلْتُ مَا لَكَ يَا رَسُولَ اللَّهِ . قَالَ " شَهِدْتُ قَتْلَ الْحُسَيْنِ آنِفًا " . هَذَا حَدِيثٌ غَرِيبٌ .
sunnah.com