Muwatta Imam Malik Book of Tahajjud, Hadith 1

Yahya related to me from Malik from Muhammad ibn al-Munkadir from Said ibn al-Jubayr that a man who has approval (as a relater of hadith), told him that A'isha, the wife of the Prophet ﷺ said, "If a man prays in the night and sleep overcomes him during it, Allah writes for him the reward of his prayer, and his sleep is sadaqa for him."

حَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، عَنْ مُحَمَّدِ بْنِ الْمُنْكَدِرِ، عَنْ سَعِيدِ بْنِ جُبَيْرٍ، عَنْ رَجُلٍ، عِنْدَهُ رِضًا أَنَّهُ أَخْبَرَهُ أَنَّ عَائِشَةَ زَوْجَ النَّبِيِّ ﷺ أَخْبَرَتْهُ أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ " مَا مِنِ امْرِئٍ تَكُونُ لَهُ صَلاَةٌ بِلَيْلٍ يَغْلِبُهُ عَلَيْهَا نَوْمٌ إِلاَّ كَتَبَ اللَّهُ لَهُ أَجْرَ صَلاَتِهِ وَكَانَ نَوْمُهُ عَلَيْهِ صَدَقَةً " .