It wasnarrated from 'Aishah that the Prophet (ﷺ) said, concerninghowlong a woman's hem should hang down:
"A hand span." 'Aishahsaid:"This may show her calves." He said: "Then a forearm'slength." (ID)
English reference (ID): Vol. 4, Book 32, Hadith 3583 (ID)
Arabic reference (ID): Book 32, Hadith 3714 (ID)