Musannaf Ibn Abi Shayba 18:1107

Abu Bakr narrated to us, he said: Waki’ narrated to us, he said: al-Mas’udi narrated to us, from al-Qasim, who said: Umar said: "Indeed, the Qasamah (oath-taking procedure in homicide cases) only necessitates the blood money (diya), and it does not shed blood (i.e., it does not lead to the execution of the accused)."