Sahih Bukhari Volume 007, Book 062, Hadith Number 041.
Narrated By 'Uqba bin Al-Harith : I married a woman and then a black lady came to us and said, "I have suckled you both (you and your wife)." So I came to the Prophet and said, "I married so-and-so and then a black lady came to us and said to me, 'I have suckled both of you.' But I think she is a liar." The Prophet turned his face away from me and I moved to face his face, and said, "She is a liar." The Prophet said, "How (can you keep her as your wife) when that lady has said that she has suckled both of you? So abandon (i.e., divorce) her (your wife)."