Sayyiduna Ibn Abbas (may Allah be pleased with them both) said: In the time of the Messenger of Allah (peace and blessings be upon him) a man was killed whose killer could not be identified. So he (peace and blessings be upon him) ascended his pulpit and said: "O people, is a man killed while I am present among you, and it is not known who killed him? If the inhabitants of the heavens and the earth all joined together in killing one Muslim man, Allah would punish them beyond count and beyond reckoning."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 12627