Sahih al-bukhari:575 Chapter: The times of As-Salat (the prayers) and the superiority of offering Salat (prayers) in time Book 9, Hadith 51

Narrated Anas: Zaid bin Thabit said, “We took the “Suhur” (the meal taken before dawn while fasting is observed)
with the Prophet (ﷺ) and then stood up for the (morning) prayer.” I asked him how long the interval
between the two (Suhur and prayer) was. He replied, ‘The interval between the two was just sufficient
to recite fifty to Sixth ‘Ayat.”