Musnad Ahmad 1556

It was narrated that Sa’d bin Abi Waqqas said: On the day of Badr my brother ‘Umair was killed and I killed Sa"eed bin al-’As and took his sword, which was called Dhul-Kateefah, and brought it to the Prophet (ﷺ) of Allah . He said: "Go and put it with the seized booty.”I went back, feeling distress such as no one knows except Allah because of the killing of my brother and the taking of my booty. It was not long before Soorat al-Anfal was revealed and the Messenger of Allah (ﷺ) said to me: “Go and take your sword."