´Anas (bin Malik) narrated that :` Zaid bin Thabit said: "We ate Sahar with the Messenger of Allah, then we stood for the Salat." I (Anas) said: "How long was that?" He said: "About the lengthy of fifty Ayahs."
Hadith Referenceسنن ترمذي / كتاب الصيام عن رسول الله صلى الله عليه وسلم / 703