Sunan At-Tirmidhi

Aishah narrated that the Messenger of Allah (s.a.w) said:The testimony of a treacherous man is not acceptable nor a treacherous woman nor a man lashed for the Hadd nor a woman lashed nor one possessing malice of enmity nor a rehearsed witness nor the Qani of (one contracted by)the family on their behalf nor the one associating himself to other than his Wala or to other than his relatives