Sunan an-Nasai 16887
In-book no 2151أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا أَبُو عَوَانَةَ، عَنْ قَتَادَةَ، وَعَبْدِ الْعَزِيزِ، عَنْ أَنَسٍ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " تَسَحَّرُوا فَإِنَّ فِي السَّحُورِ بَرَكَةً " .
It was narrated that Anas said: "The Messenger of Allah said: 'Take Sahur, for in Sahur there is blessing." 'Ata said: "someone who heard him told me that Ibn 'Umar (said) that the Prophet said: 'Whoever fasts every day of his life, then he has not fasted."