In both of the above-mentioned forms, slavery denied equality in treatment to a cross-section of mankind. Islam categorically prohibited both channels of enslaving people. The Holy Quran says:1

Meaning that: It was not lawful for any Prophet before you, nor is it for you, to take prisoners without engaging in a war. If there is a war — and that too, religious — prisoners can be captured in the battlefield.

The condition laid down in this verse does not permit anyone to imprison the civilian population of any country where war has not been declared. Nor does it permit enslaving any citizen of the opponent who has not been part of the attacking force. The imprisonment of those who actively engage in combat is allowed because they would otherwise go back to join forces in attack.

Then Allah says in these verses that:  ‘You desire the frail goods of this world’ meaning: O Muslims, do you desire to behave like other nations and enslave their people to augment your power  nay, Allah does not want you to follow other nations. He wants to guide you to the course that is better for you in the end and entitles you to win Allah’s pleasure. God reminds Muslims that nearness to God is better than any worldly gain. And God decrees that it is better for you that you do not take any prisoners except when war is imposed on you.

This rule was strictly enforced in the early days of Islam. During the reign of Hazrat Umar(ra), a deputation from Yemen came and complained that, before the advent of Islam, they had been made into slaves without any cause by a neighbouring Christian tribe. Hazrat Umar(ra) replied that though the event took place before the Muslims were in power, he would look into the case and have them set free if their complaint was borne out by facts. In contrast to this enlightened Islamic stand, the Europeans continued to use slavery for advancing their trade and agriculture until the nineteenth century.

There is no doubt that some instances of the un-Islamic custom of slavery can be found in Islamic history; but slavery was never practised to promote domestic industry or trade.