Translation
(8) Prayer (Kitab Al-Salat): Detailed Injunctions about Witr
كتاب الوتر
(506) Chapter: How It Is Recommended To Recite (The Qur'an) With Tartil
(20) باب اسْتِحْبَابِ التَّرْتِيلِ فِي الْقِرَاءَةِ
Sunan Abi Dawud 1472 
Waki' and Ibn 'Uyainah said (explaining the meaning of taghanni):
This means that the Qur'an makes a man neglect all other things, and be content with it.
حَدَّثَنَا مُحَمَّدُ بْنُ سُلَيْمَانَ الأَنْبَارِيُّ، قَالَ قَالَ وَكِيعٌ وَابْنُ عُيَيْنَةَ يَعْنِي يَسْتَغْنِي بِهِ ‏.‏
Grade :  Sahih Maqtu' (Al-Albani) صحيح مقطوع  (الألباني)حكم :
Reference : Sunan Abi Dawud 1472
In-book reference : Book 8, Hadith 57
English translation : Book 8, Hadith 1467