Abu Dawud Book 1, Hadith Number 383.

Chapter : On the border of the clothe smeared with impurity.

Narated By Umm Salamah, Ummul Mu’minin : The slave-mother of Ibrahim ibn AbdurRahman ibn Awf asked Umm Salamah, the wife of the Prophet (PBUH): I am a woman having a long border of clothe and I walk in filthy place; (then what should I do?). Umm Salamah replied: The Apostle of Allah (peace be upon him) said: What comes after it cleanses it.