I met my uncle carrying a banner, so I asked him, "Where are you headed?"He replied, "The Messenger of Allah ﷺ has sent me to a man who married his father's wife, and he commanded me to strike off his neck and seize his property."
حدثنا عمرو بن قسيط الرقي حدثنا عبيد الله بن عمرو عن زيد بن أبي أنيسة عن عدي بن ثابت
لقيت عمي ومعه راية فقلت له أين تريد قال بعثني رسول الله ﷺ إلى رجل نكح امرأة أبيه فأمرني أن أضرب عنقه وآخذ ماله
[Its isnad is sahih] Nasai narrated it in the chapter on marriage, section on marrying what one's fathers married, hadith 3334, from the hadith of Ubaydullah bin Amr, through the same chain, and Ibn Jarud graded it sahih, hadith 681. Tirmidhi also narrated it, hadith 1362, and Ibn Majah, hadith 2607. It has other routes of transmission with Ibn Hibban, hadith 516, and Hakim, 2/191, and others besides them.