Maliks Muwatta Book 36, Hadith Number 4A.

Section : Giving Testimony.

Malik related to me that Rabia ibn Abi Abd ar-Rahman said, “An Iraqi man came before Umar ibn al-Khattab and said, ‘I have come to you because of a matter which has no beginning and no end.’ Umar said, ‘What is it?’ The man said, ‘False testimony has appeared in our land.’ Umar said, ‘Is that so?’ He said, ‘Yes.’ Umar said, ‘By Allah! A man is not detained in Islam without just witnesses.'”

Malik related to me that Umar ibn al-Khattab said, “The testimony of some one known to bear a grudge or to be unreliable is not accepted.”