Sahih al-Bukhari 5098
Narrated Aisha":
(regarding) the Verse: 'And if you fear that you shall not be able to deal justly with the orphans...' 
(4.3) It is about the orphan girl who is in the custody of a man who is her guardian, and he intends to 
marry her because of her wealth, but he treats her badly and does not manage her property fairly and 
honestly. Such a man should marry women of his liking other than her, two or three or four. 
'Prohibited to you (for marriage) are: ...your foster-mothers (who suckled you).' (4.23) Marriage is 
prohibited between persons having a foster suckling relationship corresponding to a blood relationship 
which renders marriage unlawful.
حَدَّثَنَا مُحَمَّدٌ، أَخْبَرَنَا عَبْدَةُ، عَنْ هِشَامٍ، عَنْ أَبِيهِ، عَنْ عَائِشَةَ، ‏{‏وَإِنْ خِفْتُمْ أَنْ لاَ، تُقْسِطُوا فِي الْيَتَامَى‏}‏‏.‏ قَالَتِ الْيَتِيمَةُ تَكُونُ عِنْدَ الرَّجُلِ وَهْوَ وَلِيُّهَا، فَيَتَزَوَّجُهَا عَلَى مَالِهَا، وَيُسِيءُ صُحْبَتَهَا، وَلاَ يَعْدِلُ فِي مَالِهَا، فَلْيَتَزَوَّجْ مَا طَابَ لَهُ مِنَ النِّسَاءِ سِوَاهَا مَثْنَى وَثُلاَثَ وَرُبَاعَ‏.‏