Muwatta Malik 45
Sahih Lighairihi Graded by Salim al-Hilali Book of Purity · Hadith 45 of 1,858حَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، عَنْ مُحَمَّدِ بْنِ عُمَارَةَ، عَنْ مُحَمَّدِ بْنِ إِبْرَاهِيمَ، عَنْ أُمِّ وَلَدٍ، لإِبْرَاهِيمَ بْنِ عَبْدِ الرَّحْمَنِ بْنِ عَوْفٍ أَنَّهَا سَأَلَتْ أُمَّ سَلَمَةَ زَوْجَ النَّبِيِّ صلى الله عليه وسلم فَقَالَتْ إِنِّي امْرَأَةٌ أُطِيلُ ذَيْلِي وَأَمْشِي فِي الْمَكَانِ الْقَذِرِ قَالَتْ أُمُّ سَلَمَةَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " يُطَهِّرُهُ مَا بَعْدَهُ " .
Yahya related to me from Malik from Muhammad ibn Umara from Muhammad ibn Ibrahim that the mother of the son of Ibrahim ibn Abd ar- Rahman ibn Awf questioned Umm Salama, the wife of the Prophet, may Allah bless him and grant him peace, and said, "I am a woman who wears a long skirt and (sometimes) I walk in dirty places." Umm Salama replied, "The Messenger of Allah, may Allah bless him and grant him peace, said, 'What follows (i.e. clean places) purifies it
References
Muwatta Malik 45
In-book: Book 2, Hadith 14 Source: hadith-api (fawazahmed0)