It is narrated from Uqbah bin al-Harith (may Allah be pleased with him) that a black woman came and claimed that she had nursed the two of them, meaning Uqbah (may Allah be pleased with him) and his wife. He said: He came to the Prophet (peace and blessings be upon him) and mentioned this matter to him (peace and blessings be upon him). He (peace and blessings be upon him) turned away, and the Prophet (peace and blessings be upon him) smiled and said: "And how (can it be), when it has (already) been said?"
Bukhari (may Allah have mercy on him) recorded it in his Sahih from Muhammad bin Kathir.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الرضاع / 15671