Hadith 2367
Chapter 70: The fast of the Prophet - كتاب الصيام
أَخْبَرَنَا الْقَاسِمُ بْنُ زَكَرِيَّا بْنِ دِينَارٍ، قَالَ حَدَّثَنَا حُسَيْنٌ، عَنْ زَائِدَةَ، عَنْ عَاصِمٍ، عَنِ الْمُسَيَّبِ، عَنْ حَفْصَةَ، قَالَتْ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم إِذَا أَخَذَ مَضْجَعَهُ جَعَلَ كَفَّهُ الْيُمْنَى تَحْتَ خَدِّهِ الأَيْمَنِ وَكَانَ يَصُومُ الاِثْنَيْنَ وَالْخَمِيسَ .
It was narrated that Hafsah said:
"When the Messenger of Allah would lie down, he would place his right hand under his right cheek, and he used to fast on Mondays and Thursday."
Reference : Sunan an-Nasa'i 2367
In-book reference : Book 22, Hadith 278