General Behavior (Kitab Al-Adab)
Dawud :: Book 41 : Hadith 4939
Narrated Umar ibn al-Khattab:
Masruq said: I met Umar ibn al-Khattab (Allah be pleased with him) who said: Who are you? I replied: Masruq ibn al-Ajda'. Umar then said: I heard the Apostle of Allah (peace_be_upon_him) say: al-Ajda' (mutilated) is a devil.