'Abdullah bin Shikh-kheer Radiyallahu 'Anhu says:
"I attended the noble assembly of Rasulullah Sallallahu 'Alayhi Wasallam. He was performing salaah. Because of his crying, such sound emmitted from his chest, like that of a boiling pot". (AR)
English reference (AR): Book 44, Hadith 305 (AR)
Arabic reference (AR): Book 45, Hadith 322 (AR)