سنن أبي داود

Narrated Muhayyisah:

The Messenger of Allah (ﷺ) said: If you gain a victory over the men of Jews, kill them. So Muhayyisah jumped over Shubaybah, a man of the Jewish merchants. He had close relations with them. He then killed him. At that time Huwayyisah (brother of Muhayyisah) had not embraced Islam. He was older than Muhayyisah. When he killed him, Huwayyisah beat him and said: O enemy of Allah, I swear by Allah, you have a good deal of fat in your belly from his property.