The Book of Marriage (Kitab Al-Nikah)
Muslim :: Book 8 : Hadith 3391
Judaima daughter of Wahb al-Asadiyya (Allah be pleased with her) reported that she heard Allah's Messenger (may peace be upon him) assaying: I intended to prohibit cohabitation with a suckling woman until I considered that the Romans and the Persians do it without any injury being caused to their children thereby. (Imam Muslim said: Khalaf reported it from Judamat al-'Asadiyya, but the correct wording is what has been stated by Yahya.)