وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ أَبِي بَكْرِ بْنِ نَافِعٍ، عَنْ أَبِيهِ، نَافِعٍ مَوْلَى ابْنِ عُمَرَ عَنْ صَفِيَّةَ بِنْتِ أَبِي عُبَيْدٍ، أَنَّهَا أَخْبَرَتْهُ عَنْ أُمِّ سَلَمَةَ، زَوْجِ النَّبِيِّ صلى الله عليه وسلم أَنَّهَا قَالَتْ حِينَ ذُكِرَ الإِزَارُ فَالْمَرْأَةُ يَا رَسُولَ اللَّهِ قَالَ ‏"‏ تُرْخِيهِ شِبْرًا ‏"‏ ‏.‏ قَالَتْ أُمُّ سَلَمَةَ إِذًا يَنْكَشِفُ عَنْهَا ‏.‏ قَالَ ‏"‏ فَذِرَاعًا لاَ تَزِيدُ عَلَيْهِ ‏"‏ ‏.‏

Yahya related to me from Malik from Abu Bakr ibn Nafi from hisfather Nafi, the mawla of Ibn Umar that Safiyya bint Abi Ubaydinformed him that Umm Salama, the wife of the Prophet, may Allah blesshim and grant him peace, said that when the lower garment of women wasmentioned to the Messenger of Allah, he said, "She lets it down ahandspan." Umm Salama said, "If it leaves her uncovered?" He said,"Then the length of a forearm and let her not increase it." Translation Not Available

Book Ref: Muwatta Imam Malik Book 48 Hadith 1667
Web Ref:  Muwatta Imam Malik Book 48 Hadith 13