Sunan an-Nasa'i, Book 48, Hadith 298 (In-Book) ⓘ
It was narrated from Umm Salamah that: She mentioned women's hems to the Messenger of Allah [SAW], and the Messenger of Allah [SAW] said: "Let it down a hand span." Umm Salamah said: "But that will uncover (her feet)." He said: "Let it down a forearm's length, but no more than that."
حَدَّثَنَا الْعَبَّاسُ بْنُ الْوَلِيدِ بْنِ مَزْيَدٍ، قَالَ أَخْبَرَنِي أَبِي قَالَ، حَدَّثَنَا الأَوْزَاعِيُّ، قَالَ حَدَّثَنَا يَحْيَى بْنُ أَبِي كَثِيرٍ، عَنْ نَافِعٍ، عَنْ أُمِّ سَلَمَةَ، أَنَّهَا ذَكَرَتْ لِرَسُولِ اللَّهِ صلى الله عليه وسلم ذُيُولَ النِّسَاءِ فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " يُرْخِينَ شِبْرًا " . قَالَتْ أُمُّ سَلَمَةَ إِذًا يَنْكَشِفَ عَنْهَا . قَالَ " تُرْخِي ذِرَاعًا لاَ تَزِيدُ عَلَيْهِ " .
also referenced under: Hadith 5337 (Reference) & Volume 6, Book 48, Hadith 5339 (DarusSalam)