Amr bin Dinar narrates from Ibn Abbas (may Allah be pleased with them both) concerning the saying of Allah Almighty: "And consult them in the matter" [Surah Al Imran: 159], that is, consult them in affairs. He said: (This refers to) Abu Bakr and Umar (may Allah be pleased with them both).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب آداب القاضي / 20300