The Messenger of Allah said: "An orphan is to be consulted about herself, then if she is silent that is her permission, and if she refuses, then do not authorize it (the marriage) for her" (meaning: when she attains the age of puberty and refuses it.)  

قَالَ رَسُولُ اللَّهِ ﷺ الْيَتِيمَةُ تُسْتَأْمَرُ فِي نَفْسِهَا فَإِنْ صَمَتَتْ فَهُوَ إِذْنُهَا وَإِنْ أَبَتْ فَلاَ جَوَازَ عَلَيْهَا قَالَ وَفِي الْبَابِ عَنْ أَبِي مُوسَى وَابْنِ عُمَرَ وَعَائِشَةَ