Musnad Ahmad 1153:535

Abu al-Yaman narrated to us, he said: Isma'il ibn 'Ayyash narrated to us, from al-Awza'i, from 'Abd al-Rahman ibn al-Qasim, from his father, from 'A'ishah, that a *mukātab* (a slave with a contract of manumission) of hers entered upon her with the remainder of his manumission payment. She said to him: "You shall not enter upon me after this time of yours, so you must engage in *Jihad* in the way of Allah, for I heard the Messenger of Allah, peace and blessings of Allah be upon him, say: 'No dust in the way of Allah shall ever mix with the heart of a Muslim man, except that Allah will forbid the Fire upon him.'"