Qur'an, Hadith and Scholars:Non-Muslims

O Prophet! Strive against the disbelievers and the hypocrites! Be harsh with them. Their ultimate abode is hell, a hapless journey's end. They swear by Allah that they said nothing (wrong), yet they did say the word of disbelief, and did disbelieve after their Surrender (to Allah). And they purposed that which they could not attain, and they sought revenge only that Allah by His messenger should enrich them of His bounty. If they repent it will be better for them; and if they turn away, Allah will afflict them with a painful doom in the world and the Hereafter, and they have no protecting friend nor helper in the earth.

Narrated Ikrima: Ali burnt some people and this news reached Ibn 'Abbas, who said, "Had I been in his place I would not have burnt them, as the Prophet said, 'Don't punish (anybody) with Allah's Punishment.' No doubt, I would have killed them, for the Prophet said, 'If somebody (a Muslim) discards his religion, kill him.' "

Narrated 'Ali: Whenever I tell you a narration from Allah's Apostle, by Allah, I would rather fall down from the sky than ascribe a false statement to him, but if I tell you something between me and you (not a Hadith) then it was indeed a trick (i.e., I may say things just to cheat my enemy). No doubt I heard Allah's Apostle saying, "During the last days there will appear some young foolish people who will say the best words but their faith will not go beyond their throats (i.e. they will have no faith) and will go out from (leave) their religion as an arrow goes out of the game. So, where-ever you find them, kill them, for who-ever kills them shall have reward on the Day of Resurrection."