بُلُوغُ الْمَرَامِ
Bulugh al-Maram 1155
Marriage
وَأَخْرَجَهُ أَحْمَدُ: مِنْ حَدِيثِ عَلَيٍّ فَقَالَ: { وَالْجَارِيَةُ عِنْدَ خَالَتِهَا, فَإِنَّ اَلْخَالَةَ وَالِدَةٌ } [1]
Ahmad reported it from the Hadith of 'Ali (RA), he said, "The little girl must be with her maternal aunt for the maternal aunt is (the same as) a mother."
Sunnah.com reference: Book 8, Hadith 220