Looking up the meaning of slave and slavery and their alternative words in the Arabic language (abd and aubodeiah) in both Arabic and English dictionaries, we can understand that these words are not limited to the ancient practice of selling and owning humans. In other words, a human slave, in both Arabic and English languages, has the general meaning of being under the complete domination of an influence, irrespective of the kind of that influence whether it is another human or anything else.
In all cases, the free will to reverse that influence doesn't exist. This would define slavery as a degrading and oppressive situation since it goes against our God given gift of freedom of choice. The loss of our freedom means losing our honor and dignity as humans. It would also undermine and further shatter the divine principal of equality of all humans and how our righteousness is the ONLY criterion to place us in different ranks according to God; justice wouldn't be served if we were not all equally free to choose to adhere to the divine teachings of God or not :
[17:70] We have honored the children of Adam, and provided them with rides on land and in the sea. We provided for them good provisions, and we gave them greater advantages than many of our creatures.
Freedom of Choice [33:72] We have offered the responsibility (freedom of choice) to the heavens and the earth, and the mountains, but they refused to bear it, and were afraid of it. But the human being accepted it; he was transgressing, ignorant.
[49:13] "O people, we created you from the same male and female, and rendered you distinct peoples and tribes, that you may recognize one another. The best among you in the sight of GOD is the most righteous. GOD is Omniscient, Cognizant."
It is not a surprise that God's precise and infallible choice of the Arabic words in the Quran perfectly corresponds with the above general understanding and the true definition of slavery. Our ignorance, and narrow vision can throw us off and divert us from the truth, but we cannot go wrong with the flawless, unambiguous Quran. In the following verse, 16:75, we have the divine definition of a slave based on its broad foundation which is the deprivation of free will:
[16:75] GOD cites the example of a slave who is owned, and is totally powerless, compared to one whom we blessed with good provisions, from which he gives to charity secretly and publicly. Are they equal? Praise be to GOD, most of them do not know.
The above verse is certainly not limiting slavery to the ancient practice of selling/owning humans but rather clearly describes the elements that would define a slave ; owned and powerless; a person who has no control over his/her life, and has no ability to pursue his/her own will or change his/her oppressive status for reasons that are not by any means detailed in the verse. The fact that Quran is a perpetual, guiding scripture for all generations and civilizations is actually behind the divine wisdom of not giving any specifics or details about the underlying reasons for losing that free will. It could be related to drugs or to economical, emotional, mental, medical, or physical reasons. God deliberately left it opened so that the above definition would be applicable to all styles and formats of slavery situations at all times. Based on the above divine definition, if we look around, at any time, and at every corner, we will find a slave waiting to be freed. Quran clearly discourages slavery through the emphasis of freeing slaves whenever possible as a righteous, charitable act or to atone certain offenses.
Righteousness Defined [2:177] Righteousness is not turning your faces towards the east or the west. Righteous are those who believe in GOD, the Last Day, the angels, the scripture, and the prophets; and they give the money, cheerfully, to the relatives, the orphans, the needy, the traveling alien, the beggars, and to free the slaves; and they observe the Contact Prayers (Salat) and give the obligatory charity (Zakat); and they keep their word whenever they make a promise; and they steadfastly persevere in the face of persecution, hardship, and war. These are the truthful; these are the righteous.
Distribution System for Charities [9:60] Charities shall go to the poor, the needy, the workers who collect them, the new converts, to free the slaves, to those burdened by sudden expenses, in the cause of GOD, and to the traveling alien. Such is GOD's commandment. GOD is Omniscient, Most Wise.
[90:12] Which one is the difficult path?
[90:13] The freeing of slaves.
You Shall Not Kill [4:92] No believer shall kill another believer, unless it is an accident. If one kills a believer by accident, he shall atone by freeing a believing slave, and paying a compensation to the victim's family, unless they forfeit such a compensation as a charity. If the victim belonged to people who are at war with you, though he was a believer, you shall atone by freeing a believing slave. If he belonged to people with whom you have signed a peace treaty, you shall pay the compensation in addition to freeing a believing slave. If you cannot find* a slave to free, you shall atone by fasting two consecutive months, in order to be redeemed by GOD. GOD is Knower, Most Wise.
Do Not Take God's Name in Vain [5:89] GOD does not hold you responsible for the mere utterance of oaths; He holds you responsible for your actual intentions. If you violate an oath, you shall atone by feeding ten poor people from the same food you offer to your own family, or clothing them, or by freeing a slave. If you cannot afford this, then you shall fast three days. This is the atonement for violating the oaths that you swore to keep. You shall fulfill your oaths. GOD thus explains His revelations to you, that you may be appreciative.
[58:3] Those who estrange their wives in this manner, then reconcile thereafter, shall atone by freeing a slave before resuming their sexual relations. This is to enlighten you. GOD is Cognizant of everything you do.
[58:4] If you cannot find a slave to free, you shall fast two consecutive months before resuming sexual relations. If you cannot fast, then you shall feed sixty poor people. You shall believe in GOD and His messenger. These are GOD's laws. The disbelievers have incurred a painful retribution.
Even though it is very clear that the practice of slavery goes against the divine system of our freedom and the clear ethical principles of treating one another, we find that God encourages us to free slaves rather than directly prohibiting slavery. . God knows that it is very unlikely for slavery to be a discontinued practice on this earth based on the human's aggressive nature and his thirst and passion towards authority, abuse, and control. Social injustice and violations of human rights will exist as long as man is living on this earth. Instead of just prohibiting what He knows will exist irrespective of any divine commands or legal systems, God provides us with long acting and practical approaches to abolish this social disease by constantly freeing slaves, and disrupting slavery whenever encountered.. In other words, the Most Wise practically prohibited slavery through the encouragement of freeing slaves. With no doubt, this approach is far more effective ; instead of just refraining from practicing slavery through a direct command, believers and followers of the Quran continue to redeem their souls throughout their journey on earth by freeing the slaves. This, indeed, ignites a constant cold war against slavery. Praise God.
[95:8] Is GOD not the Most Wise, of all the wise ones?
[34:1] Praise be to GOD - to whom belongs everything in the heavens and the earth; all praise is also due to Him in the Hereafter. He is the Most Wise, the Cognizant.
Peaceful Friday, salaam and God bless.