Maliks Muwatta Book 28, Hadith Number 36.
Section : Prohibition against Intercourse with a Slave-Girl who Belonged to One’s Father.
Yahya related to me from Malik that he had heard that Umar ibn al-Khattab gave his son a slave-girl and said, “Do not touch her, for I have uncovered her.”
Yayha related to me from Malik that Abd arRahman ibn al-Mujabbir said that Salim ibn Abdullah gave his son a slave-girl and said, “Do not go near her, for I wanted her, and did not act towards her.”