سنن النسائي

It was narrated from Ya'la bin Mamlak that he asked Umm Salamah, the wife of the Prophet (ﷺ) about the recitation and prayer of the Messenger of Allah (ﷺ). She said: "What do you want to know about his prayer (I.e., you can never match it)? He used to pray, then sleep for as long as he had prayed, then he would pray as long as he had slept, then he would sleep as long as he had prayed, until dawn came." Then she described to him his recitation, and she described a clear recitation in which every letter was distinct.