It is narrated from Umm Salamah (may Allah be pleased with her) that a woman asked Umm Salamah (may Allah be pleased with her): "My garment is long and I walk on dirty places." Umm Salamah (may Allah be pleased with her) replied that the Messenger of Allah (peace and blessings be upon him) said: "The earth that comes after purifies it."
Hadith Referenceمسند الإمام الشافعي / كتاب الطهارة / 32
Hadith Takhrijأخرجه الترمذي: الطهارة، باب ما جاء في الوضوء من الموطئ (143) - وأبو داود، الطهارة، باب الأذى يصيب الذيل: (383) وصححه ابن الجارود: 142.