Srimad Bhagavatam Canto 10, Chapter 77, Text 05

SB 10.77.5

evam yadunam salvanam
 nighnatam itaretaram
yuddham tri-nava-ratram tad
 abhut tumulam ulbanam
 
Translation: 
 
As the Yadus and Salva’s followers thus went on attacking one another, the tumultuous, fearsome battle continued for twenty-seven days and nights.
Srimad Bhagavatam Canto 10, Chapter 77, Text 04
Srimad Bhagavatam Canto 10, Chapter 77, Text 06-07