The Prophet ﷺ said, "A matron should not be given in marriage except after consulting her; and a virgin should not be given in marriage except after her permission." The people asked, "O Messenger of Allah ﷺ! How can we know her permission?" He said, "Her silence (indicates her permission).  

أَنَّ النَّبِيَّ ﷺ قَالَ لاَ تُنْكَحُ الأَيِّمُ حَتَّى تُسْتَأْمَرَ وَلاَ تُنْكَحُ الْبِكْرُ حَتَّى تُسْتَأْذَنَ قَالُوا يَا رَسُولَ اللَّهِ وَكَيْفَ إِذْنُهَا قَالَ أَنْ تَسْكُتَ  

I said, "O Messenger of Allah ﷺ! A virgin feels shy." He said, "Her consent is (expressed by) her silence."  

أَنَّهَا قَالَتْ يَا رَسُولَ اللَّهِ إِنَّ الْبِكْرَ تَسْتَحِي قَالَ رِضَاهَا صَمْتُهَا