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."

أَخْبَرَنَا الْقَاسِمُ بْنُ زَكَرِيَّا بْنِ دِينَارٍ، قَالَ حَدَّثَنَا حُسَيْنٌ، عَنْ زَائِدَةَ، عَنْ عَاصِمٍ، عَنِ الْمُسَيَّبِ، عَنْ حَفْصَةَ، قَالَتْ كَانَ رَسُولُ اللَّهِ ﷺ إِذَا أَخَذَ مَضْجَعَهُ جَعَلَ كَفَّهُ الْيُمْنَى تَحْتَ خَدِّهِ الأَيْمَنِ وَكَانَ يَصُومُ الاِثْنَيْنَ وَالْخَمِيسَ .