There is a verse in Surat Al-Hujurat in the Koran. It is in chapter 49, verse 9: “If two parties among the Believers fall into a quarrel make ye peace between them: but if one of them transgresses beyond bounds against the other then fight ye (all) against the one that transgresses until it complies with the command of Allah; but if it complies then make peace between them with justice and be fair: for Allah loves those who are fair (and just).”
The Arabic root word “qatal”, translated here in English as “fight”, actually denotes “to kill, massacre, slaughter”. (wikiislam.net)
A footnote to this verse on the Alim.org website has this: “Individual quarrels are easier to compose than group quarrels, or, in the modern world, national quarrels. But the collective community of Islam should be supreme over groups or nations. It would be expected to act justly and try to compose the quarrel, for peace is better than fighting. But if one party is determined to be the aggressor, the whole force of the community is brought to bear on it. The essential condition of course is that there should be perfect fairness and justice and respect for the highest principles; for Islam takes account of every just and legitimate interest without separating spiritual from temporal matters. The League of Nations failed because these essentials were absent and today the United Nations fails for the same reason.”
In a letter published in 2007, entitled “A Common Word Between Us and You”, Muslims appealed to Christians to agree to dialogue based on what the “moderate” Muslims consider common between Islam and Christianity: “Muslims and Christians together make up well over half of the world’s population. Without peace and justice between these two religious communities, there can be no meaningful peace in the world. The future of the world depends on peace between Muslims and Christians.
“The basis for this peace and understanding already exists. It is part of the very foundational principles of both faiths: love of the One God, and love of the neighbour. These principles are found over and over again in the sacred texts of Islam and Christianity. The Unity of God, the necessity of love for Him, and the necessity of love of the neighbour is thus the common ground between Islam and Christianity.”
Many Christian leaders positively responded to this Muslim interfaith initiative, and have continued to pursue a way which may look good to man, but whose end will only bring death to those who refuse to submit to Islam’s definition of justice, mercy, and love.
What is common between a commandment to disciples to fight to the death those who do not submit in mutual fighting, or a quarrel (think Sunni vs Shia vs ISIS, for examples) — whether between individuals, within family, tribally, nationally, religiously — and between the commandment by the Holy One of God, the Messiah and Son of the Father, who commands His disciples to love your enemy?!
“You have heard that it was said, ‘You shall love your neighbor and hate your enemy.’ But I say to you, love your enemies, bless those who curse you, do good to those who hate you, and pray for those who spitefully use you and persecute you, that you may be sons of your Father in heaven; for He makes His sun rise on the evil and on the good, and sends rain on the just and on the unjust. For if you love those who love you, what reward have you? Do not even the tax collectors do the same? And if you greet your brethren only, what do you do more than others? Do not even the tax collectors do so? Therefore you shall be perfect, just as your Father in heaven is perfect.” (Mt 5:43-48 New Testament)