Musannaf Ibn Abi Shayba 18:969

Abu Bakr narrated to us, he said: Abdullah ibn Numayr narrated to us, from Yahya ibn Sa'id, from Sa'id ibn al-Musayyib, that a person was killed in San'a, and Umar killed seven people for him. And he said: "If the people of San'a had conspired together against him, I would have killed them all for him."