The Ansari who captured Abu Aziz ibn Umayr RA

This unnamed man of the Ansar captured Abu Aziz ibn Umayr at Badr in 2 AH. Abu Aziz's own brother Mus'ab ibn Umayr RA told him to guard his prisoner well, since their mother would pay a rich ransom, saying that the Ansari, not Abu Aziz, was his brother.