Muwatta Malik 548

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

Reference

Muwatta Malik 548

In-book

Book 16, Hadith 29