Al-Sha'bi (may Allah have mercy on him) said: Sayyiduna Ali (may Allah be pleased with him) went out to the market, and there was a Christian selling a coat of mail. Sayyiduna Ali (may Allah be pleased with him) recognised the coat of mail and said: "This is my coat of mail; between me and you is the judge of the Muslims." The judge of the Muslims was Shurayh, whom Sayyiduna Ali (may Allah be pleased with him) had appointed as judge. When Judge Shurayh (may Allah have mercy on him) saw the Commander of the Believers, he stood up from his seat of judgement, seated Sayyiduna Ali (may Allah be pleased with him) in his place, and Judge Shurayh (may Allah have mercy on him) sat in front of him beside the Christian. Sayyiduna Ali (may Allah be pleased with him) said: "O Shurayh! If my opponent were a Muslim, I would have sat with him in the place of the litigant. But I heard the Messenger of Allah (peace and blessings be upon him) say: 'Do not shake hands with them, do not initiate the greeting of salam with them, do not visit their sick, do not offer the funeral prayer over them, force them to the narrow parts of the roads, and humble them as Allah has humbled them.' Judge between me and him, O Shurayh!" Shurayh (may Allah have mercy on him) said: "Speak, O Commander of the Believers." Sayyiduna Ali (may Allah be pleased with him) said: "This coat of mail of mine went missing from me a long time ago." Judge Shurayh (may Allah have mercy on him) said: "What do you say, O Christian?" The Christian said: "I do not call the Commander of the Believers a liar, but the coat of mail is mine."
Judge Shurayh (may Allah have mercy on him) said: "I do not see that it should be taken out of his hand. Do you have any evidence?" Sayyiduna Ali (may Allah be pleased with him) said: "Shurayh has spoken the truth." The Christian said: "These are the rulings of the prophets: the Commander of the Believers comes to his own judge, and his judge rules against him. By Allah, O Commander of the Believers, this coat of mail is yours. I followed you from the army, and it had fallen off your ash-coloured camel, so I took it. I bear witness that there is no god but Allah and that Muhammad (peace and blessings be upon him) is the Messenger of Allah." Sayyiduna Ali (may Allah be pleased with him) said: "Now that you have become a Muslim, it is yours." He also gave him a horse to ride. Al-Sha'bi (may Allah have mercy on him) said: I saw him fighting the polytheists.
(b) In the narration of Ibn Abdan he said: "O Shurayh! Had my opponent not been a Christian, I would have knelt before you." At the end it says: Sayyiduna Ali (may Allah be pleased with him) gifted the coat of mail to him and fixed a stipend of two thousand for him, and he was killed (as a martyr) with him on the day of Siffin.
It has also been narrated through another, weak, route from al-A'mash, from Ibrahim al-Taymi.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب آداب القاضي / 20465