It is a manifestation of the dignity of man that Islam has placed an infinite value on human life. This is expressed in the Qur’an in the following terms:
We ordained for the children of Israel that if anyone slew a person, unless it be for murder or for spreading mischief in the land, it would be as if he slew the whole of mankind. And if anyone saved a life, it would be as if he saved the life of a whole people. (al-Ma’ida, 5:32)
The reference to the children of Israel, that is, the Jews, represents continuity of the basic values that are common to all revealed religions. Both Judaism and Islam are committed to the protection of human life. It makes no difference whether the victim is a Jew, a Muslim or anyone else. The value that is advocated is holistic and indivisible in that aggression against one is tantamount to aggression against all. Life is not only of infinite value, it is also sacred: “Nor take life which God has made sacred, except for a just cause” (al-Isra’, 17:33).
Al-Ghazali has quoted these ayat and drew the conclusion that “in respect of the sanctity of life and the prohibition of aggression against it, Muslims and non-Muslims are equal. Attack on the personal safety of non-Muslims invokes the same punishment in this world and the Hereafter”. [Muhammad Al-Ghazali, Huquq al-Insan, p. 54]
In times of military engagement, the warriors are under a personal duty not to destroy civilian life.
It is consequently unlawful to attack women and children, the elderly and the insane, the ill and the invalid and this include the blind, the lame, the crippled and the unconscious. The exempted categories also include the priest and the monk and those engaged in worship as I well as farmers who occupy themselves with their works in the field provided that they are not involved in the conflict.
The hadith contains detailed instructions on all of these and the Prophet has generally advised military commanders and soldiers in the battlefield to be fair, avoid excessive violence and incline toward peace. (Zuhaili has quoted five hadiths on the subject. See for details, Zuhaili, al-Fiqh al-Islami wa Adillatuh, VI, 421 ff.)