"Protect yourselves from the Fire, even with half a date." (Using translation from Nasāʾī 2552)  

عَنِ النَّبِيِّ ﷺ قَالَ «اتَّقُوا النَّارَ وَلَوْ بِشِقِّ تَمْرَةٍ»  

"The Messenger of Allah mentioned the Fire, and he turned his face away (as if seeing it), and sought refuge with Allah from it." (One of the narrators) Shu'bah said: "He did that three times, then he said: 'Protect yourselves from the Fire even with half a date, and if you cannot find that, then with a good word."' (Using translation from Nasāʾī 2553)  

ذَكَرَ رَسُولُ اللهِ ﷺ النَّارَ فَأَشَاحَ بِوَجْهِهِ وَتَعَوَّذَ مِنْهَا ذَكَرَ شُعْبَةُ أَنَّهُ فَعَلَهُ ثَلَاثَ مَرَّاتٍ ثُمَّ قَالَ «اتَّقُوا النَّارَ وَلَوْ بِشِقِّ تَمْرَةٍ فَإِنْ لَمْ تَجِدُوا فَبِكَلِمَةٍ طَيِّبَةٍ»