Sahih Muslim Book 8, Hadith Number 3275.

Chapter: It is forbidden to combine a woman and her father’s sister or a woman and her mother’s sister together in marriage.

Abu Huraira (Allah be pleased with him) reported that Allah’s Messenger (May peace be upon him) forbade the combining of a woman in marriage with her father’s sister, or with her mother’s sister, or that a woman should ask for divorce for her sister in order to deprive her of what belongs to her. Allah, the Exalted and Majestic, is her sustainer too.