Sahih Bukhari Volume 007, Book 062, Hadith Number 029.
Narrated By 'Ursa : That he asked 'Aisha regarding the Verse: 'If you fear that you shall not be able to deal justly with the orphans (4.3) She said, "O my nephew! This Verse refers to the orphan girl who is under the guardianship of her guardian who likes her beauty and wealth and wishes to (marry her and) curtails her Mahr. Such guardians have been forbidden to marry them unless they do justice by giving them their full Mahr, and they have been ordered to marry other than them. The people asked for the verdict of Allah's Apostle after that, so Allah revealed: 'They ask your instruction concerning the women... whom you desire to marry.' (4.127) So Allah revealed to them that if the orphan girl had beauty and wealth, they desired to marry her and for her family status. They can only marry them if they give them their full Mahr. And if they had no desire to marry them because of their lack of wealth and beauty, they would leave them and marry other women. So, as they used to leave them, when they had no interest, in them, they were forbidden to marry them when they had such interest, unless they treated them justly and gave them their full Mahr Apostle said, 'If at all there is evil omen, it is in the horse, the woman and the house." a lady is to be warded off. And the Statement of Allah: 'Truly, among your wives and your children, there are enemies for you (i.e. may stop you from the obedience of Allah)' (64.14)