Sahih al-Bukhari 6511
Narrated `Aisha:
Some rough bedouins used to visit the Prophet (ﷺ) and ask him, "When will the Hour be?" He would look 
at the youngest of all of them and say, "If this should live till he is very old, your Hour (the death of 
the people addressed) will take place." Hisham said that he meant (by the Hour), their death.
حَدَّثَنِي صَدَقَةُ، أَخْبَرَنَا عَبْدَةُ، عَنْ هِشَامٍ، عَنْ أَبِيهِ، عَنْ عَائِشَةَ، قَالَتْ كَانَ رِجَالٌ مِنَ الأَعْرَابِ جُفَاةً يَأْتُونَ النَّبِيَّ صلى الله عليه وسلم فَيَسْأَلُونَهُ مَتَى السَّاعَةُ، فَكَانَ يَنْظُرُ إِلَى أَصْغَرِهِمْ فَيَقُولُ ‏
"‏ إِنْ يَعِشْ هَذَا لاَ يُدْرِكْهُ الْهَرَمُ حَتَّى تَقُومَ عَلَيْكُمْ سَاعَتُكُمْ ‏"‏‏.‏ قَالَ هِشَامٌ يَعْنِي مَوْتَهُمْ‏.‏