Imam al-Bukhari (may Allah have mercy on him) said: "Sayyiduna Uthman (may Allah be pleased with him) accepted the invitation of a slave of al-Mughirah bin Shu'bah (may Allah be pleased with him)."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب آداب القاضي / Q20294