Sunan an-Nasa'i, Volume 3, Book 22, Hadith 2168 (DarusSalam) ⓘ
It was narrated that 'Amr bin Al-As said: "The Messenger of Allah said: 'The difference between our fasting and the fasting of the people of the Book, is eating Sahur."' '
أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا اللَّيْثُ، عَنْ مُوسَى بْنِ عُلَىٍّ، عَنْ أَبِيهِ، عَنْ أَبِي قَيْسٍ، عَنْ عَمْرِو بْنِ الْعَاصِ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " إِنَّ فَصْلَ مَا بَيْنَ صِيَامِنَا وَصِيَامِ أَهْلِ الْكِتَابِ أَكْلَةُ السُّحُورِ " .
also referenced under: Hadith 2166 (Reference) & Book 22, Hadith 77 (In-Book)