Musannaf Ibn Abi Shaybah 24347 — Those whose testimony is not

It is narrated from Talhah bin Abdullah bin Awf that the Prophet (peace and blessings be upon him) ordered a caller to make an announcement. He called out to the people until he reached al-Thaniyyah: "O people, take heed: the testimony of an adversary or of a suspected person is not acceptable, and indeed the oath is upon the defendant."