حَدَّثَنَا مُسْلِمُ بْنُ إِبْرَاهِيمَ، حَدَّثَنَا أَبَانُ، حَدَّثَنَا يَحْيَى، عَنْ أَبِي سَلَمَةَ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ النَّبِيَّ صلى الله عليه وسلم قَالَ ‏"‏ لاَ تُنْكَحُ الثَّيِّبُ حَتَّى تُسْتَأْمَرَ وَلاَ الْبِكْرُ إِلاَّ بِإِذْنِهَا ‏"‏ ‏.‏ قَالُوا يَا رَسُولَ اللَّهِ وَمَا إِذْنُهَا قَالَ ‏"‏ أَنْ تَسْكُتَ ‏"‏ ‏.‏

Abu Hurairah reported the Prophet(PBUH) as saying “ A woman who has been previously married should not be married until her permission is asked nor should a virgin be married without her permission. “They (the people) asked “What is her permission, Apostle of Allaah(PBUH)? He replied “it is by her keeping silence.” Translation Not Available

Book Ref: Sunan Abi Dawud Book 12 Hadith 2092
Web Ref:  Sunan Abi Dawud Book 11 Hadith 2087