"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. (Using translation from Nasāʾī 1214)  

أَتَيْتُ النَّبِيَّ ﷺ «وَهُوَ يُصَلِّي وَلِجَوْفِهِ أَزِيزٌ كَأَزِيزِ الْمِرْجَلِ يَعْنِي يَبْكِي»