Musannaf Ibn Abi Shaybah 31030 — Book of the Judgments

Imam al-Zuhri said: Umar bin Abd al-Aziz called me and asked about qasamah (the oaths in an unsolved killing), and said: "It occurs to me that I should abolish it, because a Bedouin comes and testifies, and likewise a man who was absent from the scene comes and testifies." Imam al-Zuhri said: I said: "O Commander of the Faithful, it is not within your power to abolish it, for the Messenger of Allah (peace and blessings be upon him) himself and the Rightly Guided Caliphs after him ruled by it."