حَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، عَنِ ابْنِ شِهَابٍ، أَنَّ عُبَيْدَ اللَّهِ بْنَ عَبْدِ اللَّهِ بْنِ عُتْبَةَ بْنِ مَسْعُودٍ، أَخْبَرَهُ أَنَّ عَبْدَ اللَّهِ بْنَ مَسْعُودٍ ابْتَاعَ جَارِيَةً مِنِ امْرَأَتِهِ زَيْنَبَ الثَّقَفِيَّةِ وَاشْتَرَطَتْ عَلَيْهِ أَنَّكَ إِنْ بِعْتَهَا فَهِيَ لِي بِالثَّمَنِ الَّذِي تَبِيعُهَا بِهِ فَسَأَلَ عَبْدُ اللَّهِ بْنُ مَسْعُودٍ عَنْ ذَلِكَ عُمَرَ بْنَ الْخَطَّابِ فَقَالَ عُمَرُ بْنُ الْخَطَّابِ لاَ تَقْرَبْهَا وَفِيهَا شَرْطٌ لأَحَدٍ ‏.‏

Yahya related to me from Malik from Ibn Shihab that Ubaydullahibn Abdullah ibn Utba ibn Masud told him that Abdullah ibn Masudbought a slave-girl from his wife, Zaynab Ath Thaqafiyya. She made acondition to him, that if he bought her, she could always buy her backfor the price that he paid. Abdullah ibn Masud asked Umar ibn al-Khattab about that and Umar ibn al-Khattab said, "Do not go near herwhile anyone has a condition concerning her over you." Translation Not Available

Book Ref: Muwatta Imam Malik Book 31 Hadith 1297
Web Ref:  Muwatta Imam Malik Book 31 Hadith 5