Musannaf Ibn Abi Shayba 18:1161

Abu Bakr narrated to us, he said: Waki’ narrated to us, from Sufyan, from al-Mughirah ibn al-Nu’man, from Hani ibn Hizam—Yahya ibn Adam added in it from Malik ibn Anas from Hani ibn Hizam—that a man found a man with his wife, so he killed her. He wrote regarding it to Umar. Umar wrote two letters regarding it: a letter for the public [stating] that he is to be executed, and a letter for the secret [stating] that the blood money is to be taken.