Sahih Bukhari Volume 5, Book 62, Hadith 3741

فَقَصَّتْهَا حَفْصَةُ عَلَى النَّبِيِّ صلى الله عليه وسلم فَقَالَ ‏"‏ نِعْمَ الرَّجُلُ عَبْدُ اللَّهِ، لَوْ كَانَ يُصَلِّي بِاللَّيْلِ ‏"‏‏.‏ قَالَ سَالِمٌ فَكَانَ عَبْدُ اللَّهِ لاَ يَنَامُ مِنَ اللَّيْلِ إِلاَّ قَلِيلاً‏.‏

who, in her turn, narrated it to the Prophet. He said, "What an excellent man Abdullah is if he only observes the night prayer." (Salim, a sub-narrator said, "Abdullah used not to sleep at night but very little hence forward."