Sahih al-Bukhari 1922
Sahih al-Bukhari · Book 30: Fasting · Sahur is a blessing but it is not compulsory
Narrated `Abdullah:
حَدَّثَنَا مُوسَى بْنُ إِسْمَاعِيلَ ، حَدَّثَنَا جُوَيْرِيَةُ ، عَنْ نَافِعٍ ، عَنْ عَبْدِ اللَّهِ ـ رضى الله عنه ـ أَنَّ النَّبِيَّ صلى الله عليه وسلم وَاصَلَ فَوَاصَلَ النَّاسُ فَشَقَّ عَلَيْهِمْ، فَنَهَاهُمْ. قَالُوا إِنَّكَ تُوَاصِلُ. قَالَ " لَسْتُ كَهَيْئَتِكُمْ، إِنِّي أَظَلُّ أُطْعَمُ وَأُسْقَى " .
The Prophet (ﷺ) fasted for days continuously; the people also did the same but it was difficult for them. So, the Prophet (ﷺ) forbade them (to fast continuously for more than one day). They slid, "But you fast without break (no food was taken in the evening or in the morning)." The Prophet (ﷺ) replied, "I am not like you, for I am provided with food and drink (by Allah).