Sunan Abi Dawud Book 42, Hadith 60
The prophet (ﷺ) went out during the time of (treaty of) al-Hudaibiyyah. He then mentioned the rest of the tradition. He said : ‘Urwah b. Mas’ud then came to him and began to speak to the Prophet (ﷺ). Whenever he talk to him, he caught his beard ; and al-Mughirah b. Shu’bah was standing near the head of the Prophet (ﷺ) with a sword with him and a helmet on him. He then struck his hand with the handle of the sword, saying : Keep away your hand from his beard. ‘Urwah then raised his head and said : Who is this ? The prophet said : Al-Mughirah b. Shu’bah.
Perhaps Allah, and Ibn Sinan’s version has : Allah looked at the participants of the battle of Badr (with mercy) and said : Do whatever you wish ; I have forgiven you.
Al-Aqra', the mu'adhdhin (announcer) of Umar ibn al-Khattab said: Umar sent me to a bishop and I called him.
Umar said to him: Do you find me in the Book? He said: Yes. He asked: How do you find me? He said: I find you (like a) castle. Then he raised a whip to him, saying: What do you mean by castle? He replied: An iron castle and severely trustworthy. He asked: How do you find the one who will come after me? He said: I find him a pious caliph, except that he will prefer his relatives. Umar said: May Allah have mercy on Uthman: He said it three times. He then asked: How do you find the one who will come after him?
He replied: I find him like rusty iron. Umar then put his hand on his head, and said: O filthy! O filthy! He said: Commander of the Faithful! He is a pious caliph, but when he is made caliph, the sword will be unsheathed and blood will be shed.
Abu Dawud said: Al-dafr means filth or evil smell.