Musannaf Ibn Abi Shayba 18:1108

Abu Bakr narrated to us, he said: Abd al-Salam ibn Harb narrated to us, from Amr, from al-Hasan, that: Abu Bakr, Umar, and the first group (of the Companions) did not execute (anyone) based on al-qasamah (the oath-based procedure for homicide).