The Messenger of Allah ﷺ gave licence to the Mothers of the believers (i.e. the wives of the Prophet) to hang down their lower garment a span. Then they asked him to increase it, and he increased one span for them. They would send (the garment) to us and we would measure it one forearm's length for them.
رَخَّصَ رَسُولُ اللَّهِ ﷺ لأُمَّهَاتِ الْمُؤْمِنِينَ فِي الذَّيْلِ شِبْرًا ثُمَّ اسْتَزَدْنَهُ فَزَادَهُنَّ شِبْرًا فَكُنَّ يُرْسِلْنَ إِلَيْنَا فَنَذْرَعُ لَهُنَّ ذِرَاعًا
The Messenger of Allah ﷺ gave licence to the Mothers of the believers (i.e. the wives of the Prophet) to hang down their lower garment a span. Then they asked him to increase it, and he increased one span for them. They would send (the garment) to us and we would measure it one forearm's length for them. (Using translation from Abū Dāʾūd 4119)
رَخَّصَ رَسُولُ اللهِ ﷺ لِأُمَّهَاتِ الْمُؤْمِنِينَ فِي الذَّيْلِ شِبْرًا فَاسْتَزَدْنَهُ فَزَادَهُنَّ شِبْرًا آخَرَ فَجَعَلْنَهُ ذِرَاعًا فَكُنَّ يُرْسِلْنَ إِلَيْنَا نَذْرَعُ لَهُنَّ ذِرَاعًا