Amir (may Allah have mercy on him) said: There was a dispute between Sayyiduna Umar and Sayyiduna Ubayy (may Allah be pleased with them both) about a garden. Sayyiduna Umar (may Allah be pleased with him) made Sayyiduna Zayd bin Thabit (may Allah be pleased with him) the arbiter. The two of them went, and Sayyiduna Zayd (may Allah be pleased with him) recognised his voice, opened the door and said: "O Commander of the Faithful! Had you sent someone, I would have come to you." Sayyiduna Umar (may Allah be pleased with him) said: "The arbiter is come to in his own house."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب آداب القاضي / 20512