Delaying the Predawn Meal

Anas bin Malik narrated that Zaid bin Thabit (radi Allahu anhuma) said: "We ate Sahur with the Messenger of Allah (sal Allahu alaihi wa sallam), then we stood for the Salat." I (Anas) asked: "How long was that?" He replied: "About the length of fifty ayaat." [Jami at-Tirmidhi - sahih hadith]

Reciting fifty ayahs slowly with proper pronunciation and rules of recitation takes about five to seven minutes. Accordingly, it may be said that the interval between Rasul Allah’s predawn meal (sahur) and the call to morning prayer was only five to seven minutes or less than that. A narration in Sahih Al-Bukhari is also to this effect.