Musannaf Ibn Abi Shayba 36:166

Abu Usama narrated to us, he said: Sulayman ibn al-Mughira narrated to me, he said: Thabit narrated to us, he said: "Umar ibn al-Khattab had a spear on the day of Badr, and no captive was brought to him except that he would thrust it into him." He said: "When al-Abbas was taken, he said to his captor: 'Do you know who I am?' He said: 'No.' He said: 'I am the uncle of the Messenger of Allah, may Allah bless him and grant him peace, so do not take me to Umar.' He said: 'So he held him back.'" "And Aqil was taken, and he said to his captor: 'Do you know who I am?' He said: 'No.' He said: 'I am the cousin of the Messenger of Allah, may Allah bless him and grant him peace.' He said: 'So the people held back.'"