Musannaf Ibn Abi Shaybah

Hazrat Ata narrates that a man was brought to Hazrat Ali (may Allah be pleased with him) and two witnesses testified against him that he had committed theft. Then Hazrat Ali became engaged in some other matter among the people's affairs and he scolded the false witnesses and said: "No false witness should be brought to me, otherwise I will deal with him in such and such a manner." The narrator said: Then Hazrat Ali called for those two witnesses but did not find them, so he set that man free.