It is narrated from Sayyiduna al-Mughirah bin Shu'bah (may Allah be pleased with him) that he was standing by the head of the Prophet (peace and blessings be upon him) holding a sword, with his face covered by a cloth. Urwah, while speaking, began reaching out his hand towards the blessed beard of the Messenger of Allah (peace and blessings be upon him). Al-Mughirah (may Allah be pleased with him) said to him: Hold back your hand, or else it will not return to you - and al-Mughirah (may Allah be pleased with him) had a sword hanging from his shoulder. Urwah said: O Messenger of Allah, who is this? He (peace and blessings be upon him) said: "This is your nephew, al-Mughirah." Urwah said: O treacherous one! I have still not washed my head of your treachery.
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 18088