Language:
كتاب الصوم
30  
Fasting
(19)
Chapter: Interval between the Sahur and Salat-ul-Fajr
(19)
باب قَدْرِ كَمْ بَيْنَ السَّحُورِ وَصَلاَةِ الْفَجْرِ
Sahih al-Bukhari 1921

Narrated Anas:

Zaid bin Thabit said, "We took the Suhur with the Prophet (ﷺ) . Then he stood for the prayer." I asked, "What was the interval between the Suhur and the Adhan?" He replied, "The interval was sufficient to recite fifty verses of the Qur'an."

حَدَّثَنَا مُسْلِمُ بْنُ إِبْرَاهِيمَ، حَدَّثَنَا هِشَامٌ، حَدَّثَنَا قَتَادَةُ، عَنْ أَنَسٍ، عَنْ زَيْدِ بْنِ ثَابِتٍ ـ رضى الله عنه ـ قَالَ تَسَحَّرْنَا مَعَ النَّبِيِّ صلى الله عليه وسلم ثُمَّ قَامَ إِلَى الصَّلاَةِ‏.‏ قُلْتُ كَمْ كَانَ بَيْنَ الأَذَانِ وَالسَّحُورِ قَالَ قَدْرُ خَمْسِينَ آيَةً‏.‏
Reference : Sahih al-Bukhari 1921
In-book reference : Book 30, Hadith 30
USC-MSA web (English) reference : Vol. 3, Book 31, Hadith 144
  (deprecated numbering scheme)