Al-Hasan (may Allah have mercy on him) said that a man came to Sayyiduna Ali (may Allah be pleased with him) in Kufah, then he came as a party to a dispute. Sayyiduna Ali (may Allah be pleased with him) asked: "Are you a party to a dispute?" He said: "Yes." He said: "Then go, for the Messenger of Allah (peace and blessings be upon him) forbade 'that we host a party to a dispute unless his opponent is also present.'"
Hadith Referenceالسنن الكبرى للبيهقي / كتاب آداب القاضي / 20470