Sahih Bukhari Volume 8, Book 81, Hadith 6542

قَالَ الأَعْمَشُ حَدَّثَنِي عَمْرٌو، عَنْ خَيْثَمَةَ، عَنْ عَدِيِّ بْنِ حَاتِمٍ، قَالَ قَالَ النَّبِيُّ صلى الله عليه وسلم ‏"‏ اتَّقُوا النَّارَ ‏"‏‏.‏ ثُمَّ أَعْرَضَ وَأَشَاحَ، ثُمَّ قَالَ ‏"‏ اتَّقُوا النَّارَ ‏"‏‏.‏ ثُمَّ أَعْرَضَ وَأَشَاحَ ثَلاَثًا، حَتَّى ظَنَنَّا أَنَّهُ يَنْظُرُ إِلَيْهَا، ثُمَّ قَالَ ‏"‏ اتَّقُوا النَّارَ وَلَوْ بِشِقِّ تَمْرَةٍ، فَمَنْ لَمْ يَجِدْ فَبِكَلِمَةٍ طَيِّبَةٍ ‏"‏‏.‏

Narrated By 'Adi bin Hatim : The Prophet said, "Protect yourself from the Fire." He then turned his face aside (as if he were looking at it) and said again, "Protect yourself from the Fire," and then turned his face aside (as if he were looking at it), and he said so for the third time till we thought he was looking at it. He then said, "Protect yourselves from the Fire, even if with one half of a date and he who hasn't got even this, (should do so) by (saying) a good, pleasant word."