Uwaymir came to Asim bin Adi (may Allah be pleased with him), who was the chief of Banu al-Ajlan, and said: "What is your view about a man who finds a (strange) man with his wife: should he kill him, and then you kill him in retaliation, or what should he do?" And he said: "Ask the Messenger of Allah (peace and blessings be upon him) about this for me." So Asim went to the Prophet (peace and blessings be upon him) and said: "O Messenger of Allah! A man finds a (strange) man with his wife: should he kill him, and then you kill him in retaliation, or what should he do?" The narrator said: The Messenger of Allah (peace and blessings be upon him) disliked such questions. Uwaymir asked him (Asim), and Asim said: "The Messenger of Allah (peace and blessings be upon him) disliked such questions and found fault with them." Uwaymir said: "By Allah! I will not desist until I ask the Messenger of Allah (peace and blessings be upon him) about it myself." The narrator said: So Uwaymir came and said: "O Messenger of Allah! A man finds a (strange) man with his wife: should he kill him, and then you kill him in retaliation, or what should he do?" The Messenger of Allah (peace and blessings be upon him) said: "The Qur'an has been revealed concerning you and your companion." And the Messenger of Allah (peace and blessings be upon him) ordered them to perform li'an (mutual imprecation) as Allah has explained in His Book, so the two of them performed li'an. Then Uwaymir said: "O Messenger of Allah! If I keep her, I will have wronged her." The narrator said: Then he divorced her, and this became the practice for all those who performed li'an after them. The Messenger of Allah (peace and blessings be upon him) said: "Watch: if she gives birth to a child who is dark, with large, deep-black eyes, large buttocks and plump shins, then I think that Uwaymir has told the truth about her; and if she gives birth to a reddish child, as if he were a gecko, then I think that Uwaymir has lied against her." The narrator said: So she gave birth to the child matching the description which the Messenger of Allah (peace and blessings be upon him) had given confirming Uwaymir, and the child's lineage was attributed to his mother.
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 5656