(18) باب الْبُكَاءِ فِي الصَّلاَةِ
It was narrated from Mutarrif that his father said:
"I came to the Prophet (ﷺ) when he was praying, and there was a sound coming from his chest like the sound of water boiling," meaning, he was weeping.
Reference: Sunan an-Nasa'i 1214
In-book reference: Book 13, Hadith 36
English translation: Vol. 2, Book 13, Hadith 1215