Sahih al-Bukhari, Book 81, Hadith 152 (In-Book) ⓘ

Narrated `Adi bin Hatim: The Prophet mentioned the Fire and turned his face aside and asked for Allah's protection from it, and then again he mentioned the Fire and turned his face aside and asked for Allah's protection from it and said, "Protect yourselves from the Hell-Fire, even if with one half of a date, and he who cannot afford that, then (let him do so) by (saying) a good, pleasant word."

حَدَّثَنَا سُلَيْمَانُ بْنُ حَرْبٍ، حَدَّثَنَا شُعْبَةُ، عَنْ عَمْرٍو، عَنْ خَيْثَمَةَ، عَنْ عَدِيِّ بْنِ حَاتِمٍ، أَنَّ النَّبِيَّ صلى الله عليه وسلم ذَكَرَ النَّارَ فَأَشَاحَ بِوَجْهِهِ فَتَعَوَّذَ مِنْهَا، ثُمَّ ذَكَرَ النَّارَ فَأَشَاحَ بِوَجْهِهِ فَتَعَوَّذَ مِنْهَا، ثُمَّ قَالَ ‏ "‏ اتَّقُوا النَّارَ وَلَوْ بِشِقِّ تَمْرَةٍ، فَمَنْ لَمْ يَجِدْ فَبِكَلِمَةٍ طَيِّبَةٍ ‏" ‏‏.‏