What is the prescribed time for taking the pre-dawn meal (Suhur)?

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It is preferred to delay the Suhur until as close to the dawn prayer as possible, as this provides more strength for the fast. Imam Ahmad preferred this based on the action of Zayd ibn Thabit, who stated that the time between their Suhur with the Prophet and the prayer was equivalent to reciting fifty verses. Delaying is also supported by the Prophet calling it the "blessed meal," implying proximity to the time of need. The time limit is defined by the appearance of the true dawn, supported by the Quranic verse, "and eat and drink until the white thread of dawn becomes distinct to you from the black thread" (Quran 2:187). One should continue eating until certainty of the dawn's appearance is established, even if one is doubtful about the actual time of Fajr.