Malik related to me from Ishaq ibn Abdullah ibn Abi Talha thatAnas ibn Malik said, "I heard Umar ibn al-Khattab, when I was goingout with him to visit an orchard, say to himself, and there was a wallbetween him and me and he was inside the garden, 'Umar ibn al-Khattab,amir al-muminin! Well done! Well done! By Allah, fear Allah or he willpunish you.' " (ID)
USC-MSA web (English) reference: Book 56, Hadith 24 (ID)
Arabic reference (ID): Book 56, Hadith 1837 (ID)