When the Messenger of Allah ﷺ mentioned lower garment, Umm Salamah, wife of the Messenger of Allah ﷺ, asked him: And a woman, Messenger of Allah? He replied: She may hang down a span. Umm Salamah said: Still it (foot) will be uncovered. He said: Then a forearm's length, nor exceeding it.
أَنَّ أُمَّ سَلَمَةَ زَوْجَ النَّبِيِّ ﷺ قَالَتْ لِرَسُولِ اللَّهِ ﷺ حِينَ ذَكَرَ الإِزَارَ فَالْمَرْأَةُ يَا رَسُولَ اللَّهِ قَالَ تُرْخِي شِبْرًا قَالَتْ أُمُّ سَلَمَةَ إِذًا يَنْكَشِفُ عَنْهَا قَالَ فَذِرَاعًا لاَ تَزِيدُ عَلَيْهِ