Al-Layth (may Allah have mercy on him) said: Abu Ja'far (may Allah have mercy on him) said to me: Become governor of Egypt on my behalf. I said: O Commander of the Faithful! I am a weak man. I am one of the mawali (freedmen). He said: You are not weak; it is only your intention to work with me that is weak. Do you want greater strength than mine, and greater work than my work? He said: If you refuse, then direct me to a man to whom I can entrust the governorship of Egypt. I said: Uthman bin al-Hakam al-Judhami (may Allah have mercy on him) is a righteous man, and he has a tribe as well. When this reached him, he swore by Allah that he would never speak to al-Layth bin Sa'd (may Allah have mercy on him).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب آداب القاضي / 20236