Hadith-

In the Name of Allah, the Most Gracious, the Most Merciful.

Anas reported that the Messenger of Allah, may Allah bless him and grant him peace, said, "Have suhur. There is blessing in suhur." [Agreed upon]

Zayd ibn Thabit said, "We used to have suhur with the Prophet, may Allah bless him and grant him peace. Then he stood up for the prayer." Anas said, "I said, 'How long was there between the adhan and suhur?' He said, 'Enough to recite fifty ayats.'" [Agreed upon]

Riyad as-Salihin (The Meadows of the Righteous) of Iman Mohieddine Annawawi 631-676. Chapter 221:"The excellence of suhur and delaying it as long as one does not fear the approach of dawn ",Hadiths No. 1229 & 1230.