Musnad Ahmad 1153:2096

Muhammad ibn Bakr al-Bursani narrated to us, he said: Ubayd Allah ibn Abi Ziyad informed us, from al-Qasim ibn Muhammad, from Aisha: Sahlah bint Suhayl ibn Amr came and said: "O Messenger of Allah, Salim used to enter upon me while I had laid aside my garment, but now he enters upon me after he has grown up and matured, and I find something in myself regarding that." He said: "Breastfeed him, for that will remove what you find in yourself."