Musannaf Ibn Abi Shayba 19:804

Abu Bakr narrated to us, he said: Ibn Numayr narrated to us, from Isma'il ibn Abi Khalid, from 'Imran, from al-Sha'bi, that he was asked about four [men] who testified against a man that he is not the son of so-and-so, and four [men] testified that he is the son of so-and-so. He said: "Ward off [the punishment/claim] from these, because they are four, and believe the others."