Question: At what time should Sehri be observed during Ramadan Mubarak?
Answer: The time for eating Sehri is just before true dawn (Subh Sadiq). It is not preferable to make a habit of eating Sehri at night and then sleeping, or to finish it very early before true dawn. One should end Sehri sufficiently before true dawn to ensure with certainty that it is completed before dawn breaks.
The scholars of Fiqh have stated that if the night is divided into six parts, performing Sehri in the last sixth part is Sunnah (recommended). It should not be made a habit to do it earlier. For example, if the night is 12 hours long, performing Sehri at any time in the two hours before true dawn fulfills the recommendation, though it is more virtuous closer to the end of the time, just before true dawn. However, one should not continue eating until the Azan; food and drink should be stopped 2-4 minutes before the confirmed end of Sehri time according to reliable calendars.
Hazrat Zaid bin Thabit (may Allah be pleased with him) said: “We ate Suhur with the Messenger of Allah (peace be upon him), then he stood for prayer.” Hazrat Anas (may Allah be pleased with him) asked Hazrat Zaid bin Thabit (may Allah be pleased with him): “How much time was there between the Azan and Suhur?” Hazrat Zaid (may Allah be pleased with him) replied: “The time it takes to recite fifty verses.” (Sahih Bukhari, 1/257, old edition).
This indicates that Sehri should be ended moments before the end of the time, as the Prophet (peace be upon him) finished it that much earlier before the Azan—equivalent to reciting fifty verses—and in Ramadan Mubarak, the Fajr Azan is given right at true dawn.

