Anas bin Malik reported,

The Prophet of Allah ﷺ and Zayd bin Thabit ate their predawn meal together. When they finished, the Prophet of Allah ﷺ rose for the prayer and prayed.We asked Anas, "How long was it between their finishing the meal and beginning the prayer?"He replied, "About the time it takes a man to recite fifty verses."

Azami 4366

Sahih

عن أنس بن مالك قال

إن نبي الله ﷺ وزيد بن ثابت تسحرا، فلما فرغا من سحورهما قام نبي الله ﷺ إلى الصلاة فصلى. قلنا لأنس: كم كان بين فراغهما من سحورهما ودخولهما في الصلاة؟ قال: كقدر ما يقرأ الرجل خمسين آية.

الأعظمي 4366صحيح
Contents
Reference
Commentary
Ayat
Collection
Jami al-Kamil
Book
Fasting
Chapter
Obligation of fasting, its virtue, and its rulings
Section
Recommendation to delay suhoor until the true Fajr becomes apparent
Numbering
Jami al-Kamil 4366 (2nd edition)
Azami 4366