Mishkat al-Masabih 504

Umm Salama said that a woman told her she had a long skirt and walked in filthy places, so she told her that God’s messenger had said,
“What comes after it cleanses it.” [i.e. cleaner roads after the filthy places have been passed.]
Malik, Ahmad, Tirmidhi, Abu Dawud and Darimi transmitted it, the last two mentioning that the woman was an umm walad* belonging to Ibrahim b. ‘Abd ar-Rahman b. ‘Auf.
*Lit. “mother of a boy”. Used of a slavewoman who has borne a child to her master, and therefore gains her freedom when he dies.