(36) بَابُ مَنْ قَالَ لاَ نِكَاحَ إِلاَّ بِوَلِيٍّ
Narrated `Aisha:
(as regards the Verse): 'And about what is recited unto you in the Book, concerning orphan girls to whom you give not the prescribed portions and yet, whom you desire to marry.' (4.127) This Verse is about the female orphan who is under the guardianship of a man with whom she shares her property and he has more right over her (than anybody else) but does not like to marry her, so he prevents her, from marrying somebody else, lest he should share the property with him.
Reference: Sahih al-Bukhari 5128
In-book reference: Book 67, Hadith 64
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 7, Book 62, Hadith 59