Musnad Ahmad 1309:1

Husayn and Abu Nu'aym narrated to us, they said: Isra'il narrated to us, from Zayd ibn Jubayr, from Abu Yazid al-Danni, from Maymunah bint Sa'd, the freed slave-woman of the Prophet, may Allah bless him and grant him peace, who said: The Messenger of Allah, may Allah bless him and grant him peace, was asked about the child of zina (adultery/fornication). He said: "There is no good in him. Two sandals with which I strive in the way of Allah are more beloved to me than that I should free a child of zina."