Sunan at-Tirmithiy كتاب الصوم باب ما جاء فى تأخير السحور

حَدَّثَنَا يَحْيَى بْنُ مُوسَى حَدَّثَنَا أَبُو دَاوُدَ الطَّيَالِسِىُّ حَدَّثَنَا هِشَامٌ الدَّسْتَوَائِىُّ عَنْ قَتَادَةَ عَنْ أَنَسِ بْنِ مَالِكٍ عَنْ زَيْدِ بْنِ ثَابِتٍ قَالَ تَسَحَّرْنَا مَعَ النَّبِىِّ صلى الله عليه وسلم ثُمَّ قُمْنَا إِلَى الصَّلاَةِ. قَالَ قُلْتُ كَمْ كَانَ قَدْرُ ذَلِكَ قَالَ قَدْرُ خَمْسِينَ آيَةً.
Zayd Ibn-Thābit said, "We and the Prophet, peace and blessings of God be upon him had the pre-dawn meal (1) then got up to pray (the dawn prayer) (2)." Anas Ibn-Mālik asked Zayd, "How long was the interval?(3)" Zayd replied, "As long as [reciting] fifty verses [of the Qur'ān] (4)."
(1) Saḥūr: An optional, yet desirable meal eaten before dawn by Muslims planning to fast that day. (2) First prescribed prayer of the day that takes place before sunrise. (3) between the meal and the time for prayer. (4) Reciting fifty verses of the Qur'ān takes approximately four to six minutes, which indicates that the Prophet, peace and blessings of God be upon him, and his companions delayed their pre-dawn meal until there was only a short time before the dawn prayer (i.e. the beginning of fasting).