Muwatta Malik #558
Burials
The Arabic includes the chain of narration (sanad) and the collector's commentary; the English translation shows the Prophet's words only.
وَحَدَّثَنِي عَنْ مَالِكٍ، أَنَّهُ بَلَغَهُ أَنَّ أُمَّ سَلَمَةَ، زَوْجَ النَّبِيِّ صلى الله عليه وسلم كَانَتْ تَقُولُ مَا صَدَّقْتُ بِمَوْتِ النَّبِيِّ صلى الله عليه وسلم حَتَّى سَمِعْتُ وَقْعَ الْكَرَازِينِ .
Yahya related to me from Malik that he had heard that Umm Salama,
the wife of the Prophet, may Allah bless him and grant him peace, used
to say, "I did not believe that the Messenger of Allah, may Allah
bless him and grant him peace, had died until I heard the pickaxes
fall."
About Muwatta Malik
This hadith is #558 from Muwatta Malik, in the Book of Burials.