Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) said: "When the righteous are mentioned, then be sure to mention Umar (may Allah be pleased with him). Indeed, his acceptance of Islam was a help, and his leadership was a victory. By Allah, I know of nothing on earth that did not feel the loss of Umar (may Allah be pleased with him), even the thorny trees. By Allah, I think that between his eyes there was an angel who kept him on the right path and guided him. By Allah, I think that Satan feared introducing any innovation into Islam lest Umar (may Allah be pleased with him) reject it. And by Allah, if I came to know that even a dog loved Umar (may Allah be pleased with him), I would love it too."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 8781