al-Bara' bin Azib bin al-Harith · The Book of Marriage

"The rest of the wives of the Prophet refused for anyone to enter upon them on the basis of that type of breast-feeding, meaning breast-feeding of an adult. They said to 'Aishah: 'By Allah, we think that this is a concession which the Messenger of Allah granted only to Salim. No one will enter upon us, nor see us on the basis of this type of breast-feeding.'"