NASAI-KUBRA 1136:
from Muṭarrif from his father —
"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)
الكبرى للنسائي ١١٣٦:
عن مطرف عن أبيه —
أَتَيْتُ النَّبِيَّ ﷺ «وَهُوَ يُصَلِّي وَلِجَوْفِهِ أَزِيزٌ كَأَزِيزِ الْمِرْجَلِ يَعْنِي يَبْكِي»