حَدَّثَنَا عُثْمَانُ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا وَكِيعٌ، حَدَّثَنَا مُحَمَّدُ بْنُ قَيْسٍ الأَسَدِيُّ، عَنِ الْحَكَمِ بْنِ عُتَيْبَةَ، عَنْ سَعِيدِ بْنِ جُبَيْرٍ، عَنِ ابْنِ عَبَّاسٍ، قَالَ ‏:‏ بِتُّ عِنْدَ خَالَتِي مَيْمُونَةَ فَجَاءَ رَسُولُ اللَّهِ صلى الله عليه وسلم بَعْدَ مَا أَمْسَى فَقَالَ ‏:‏ ‏"‏ أَصَلَّى الْغُلاَمُ ‏"‏ ‏.‏ قَالُوا ‏:‏ نَعَمْ ‏.‏ فَاضْطَجَعَ حَتَّى إِذَا مَضَى مِنَ اللَّيْلِ مَا شَاءَ اللَّهُ قَامَ فَتَوَضَّأَ، ثُمَّ صَلَّى سَبْعًا أَوْ خَمْسًا أَوْتَرَ بِهِنَّ لَمْ يُسَلِّمْ إِلاَّ فِي آخِرِهِنَّ ‏.‏

Narrated Ibn 'Abbas: I spent a night with my maternal aunt Maimunah. The Messenger of Allah (PBUH) came after the evening has come. He asked: Did the boy pray ? She said: Yes. Then he lay down till a part of night had passed as much as Allah willed; he got up, performed ablution and prayed seven or five rak'ahs, observing witr with them. He uttered the salutation only in the last of them. Translation Not Available

Book Ref: Sunan Abi Dawud Book 5 Hadith 1356
Web Ref:  Sunan Abi Dawud Book 5 Hadith 1351