Sayyiduna Abdullah (may Allah be pleased with him) says: We were sitting in the mosque on the night of Friday when a man came and began saying: "If I find someone with my wife and kill him, you will kill me; if I accuse her, you will impose the punishment for false accusation (hadd al-qadhf). I will go and tell the Prophet (peace and blessings be upon him) about this." So he came to the Prophet (peace and blessings be upon him) and mentioned this, and the verse of li'an was revealed. Then a man came and accused his wife, so he (peace and blessings be upon him) had them perform li'an between them and said: "She will give birth to a black child with curly hair." Then she gave birth to just such a child.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الأشربة والحد فيها / 17646