It is narrated from Sahl bin Sa’d (may Allah be pleased with him) that ‘Uwaymir (may Allah be pleased with him) came to ‘Asim (may Allah be pleased with him) and said: “A man finds another man with his wife and kills him; then will you also kill him in retribution? So what should that man do? ‘Asim! Ask the Messenger of Allah (ﷺ) this question for me.” He asked the Prophet (ﷺ), and the Prophet (ﷺ) disliked the matter and expressed displeasure. ‘Asim (may Allah be pleased with him) came to ‘Uwaymir (may Allah be pleased with him) and informed him that the Prophet (ﷺ) disliked the matter and expressed displeasure, so ‘Uwaymir said: “By Allah! I will go to the Prophet (ﷺ) myself.” He came, and after ‘Asim (may Allah be pleased with him) had left, the Qur’an had been revealed. He came and asked the Messenger of Allah (ﷺ), so the Prophet (ﷺ) said: “The Qur’an has been revealed regarding you.” Then both of them (the husband and wife) came and performed li’an (mutual cursing). Then ‘Uwaymir (may Allah be pleased with him) said: “If I still keep her in my marriage, then it means I am a liar,” so he separated from her (i.e., divorced her), although the Prophet (ﷺ) had not commanded him to do so. Then this became the practice among those who performed li’an. And the Messenger of Allah (ﷺ) said: “Look! If she gives birth to a child with red complexion, short stature, and resembling a lizard, then I will think that her husband has slandered her, and if she gives birth to a child who is dark-skinned, with large eyes and large buttocks, then I will think that her husband has spoken the truth about her.” When the child was born, he had the disliked characteristic (i.e., he was from adultery).
Hadith Referenceمسند الإمام الشافعي / كتاب اللعان / 1331
Hadith Takhrijاخرجه البخارى، الاعتصام بالكتاب والسنة، باب ما يكره من التعمق والتنازع .... الخ (7304)۔