Their multitude will be put to flight and they will show their backs. Nay, but the Hour is their appointed time and that Hour will be more grievous and more bitter."
Al-Bukhari also recorded that Yusuf bin Mahak said,
"I was with the Mother of the faithful, A'ishah, when she said, `When I was still a young playful girl in Makkah, this Ayah was revealed to Muhammad,
بَلِ السَّاعَةُ مَوْعِدُهُمْ وَالسَّاعَةُ أَدْهَى وَأَمَرُّ
Nay, but the Hour is their appointed time and that Hour will be more grievous and more bitter."
This is the abridged narration that Al-Bukhari collected, but he also collected a longer narration of it in the Book of the Virtues of the Qur'an.
Muslim did not collect this Hadith.