Sahih Muslim
The Book of Fasting (Kitab Al-Sawm)
Book Number: 006 / Hadith Number: 2415
Zaid b. Thabit (Allah be pleased with him) said: We took meal shortly before dawn along with the Messenger of Allah (may peace be upon him). We then stood up for prayer. I said: How much span of time was there between the two (acts, i. e. taking of Sahri and observing of prayer)? He said (a span of reciting) fifty verses.