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."

حَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، أَنَّهُ بَلَغَهُ أَنَّ عُمَرَ بْنَ الْخَطَّابِ، وَهَبَ لاِبْنِهِ جَارِيَةً فَقَالَ لاَ تَمَسَّهَا فَإِنِّي قَدْ كَشَفْتُهَا ‏.‏
USC-MSA web (English) reference : Book 28, Hadith 36
Arabic reference : Book 28, Hadith 1130