Hadith 511300
Chapter 28: Marriage - كتاب النكاح
حَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، أَنَّهُ بَلَغَهُ أَنَّ عُمَرَ بْنَ الْخَطَّابِ، وَهَبَ لاِبْنِهِ جَارِيَةً فَقَالَ لاَ تَمَسَّهَا فَإِنِّي قَدْ كَشَفْتُهَا .
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."
Reference Muwatta Malik 511300
USC-MSA web (English) reference : Book 28, Hadith 36