Ibn 'Umar (RAA) narrated, 'A young boy was murdered deceitfully. 'Umar (RAA) thereupon said, 'If all the people of San'a' (in Yemen) participated in killing him, I would kill them all.' Related by al-Bukhari.
English reference: Book 9, Hadith 1215
Arabic reference: Book 9, Hadith 1185