حَدَّثَنَا مُحَمَّدُ بْنُ يَحْيَى، وَالْحَسَنُ بْنُ مُدْرِكٍ الطَّحَّانُ، قَالاَ حَدَّثَنَا يَحْيَى بْنُ حَمَّادٍ، حَدَّثَنَا أَبُو عَوَانَةَ، عَنْ دَاوُدَ بْنِ عَبْدِ اللَّهِ الأَوْدِيِّ، عَنْ عَبْدِ الرَّحْمَنِ الْمُسْلِيِّ، عَنِ الأَشْعَثِ بْنِ قَيْسٍ، قَالَ ضِفْتُ عُمَرَ لَيْلَةً فَلَمَّا كَانَ فِي جَوْفِ اللَّيْلِ قَامَ إِلَى امْرَأَتِهِ يَضْرِبُهَا فَحَجَزْتُ بَيْنَهُمَا فَلَمَّا أَوَى إِلَى فِرَاشِهِ قَالَ لِي يَا أَشْعَثُ احْفَظْ عَنِّي شَيْئًا سَمِعْتُهُ مِنْ رَسُولِ اللَّهِ ـ صلى الله عليه وسلم ـ ‏"‏ لاَ يُسْأَلُ الرَّجُلُ فِيمَ يَضْرِبُ امْرَأَتَهُ وَلاَ تَنَمْ إِلاَّ عَلَى وِتْرٍ ‏"‏ ‏.‏ وَنَسِيتُ الثَّالِثَةَ ‏.‏

It was narrated that Ash'ath bin Qais said: "I was a guest (at the home) of 'Umar one night, and in the middle of the night he went and hit his wife, and I separated them. When he went to bed he said to me: 'O Ash'ath, learn from me something that I heard from the Messenger of Allah" A man should not be asked why he beats his wife, and do not go to sleep until you have prayed the Witr."' And I forgot the third thing." Translation Not Available

Book Ref: Sunan Ibn Majah Book 9 Hadith 1986
Web Ref:  Sunan Ibn Majah Vol 3 Book 9 Hadith 1986