In the Nutshell:
Islam didn't ban slavery cause the Islamic concept of slavery is quite different one. The word "Slavery" comes up with its own luggage, depends upon the cultural and ideological connotations, one is coming from. What deemed as Slavery by someone, may or may not be deemed as Slavery by others. There isn't any monolithic understanding of Slavery or any consensus upon that. So it is important to distinguish the difference between Islamic and other variants of slavery.
Slavery, as addressed in Islam, has two separates aspects:
- the treatment of those who have already been enslaved previously, and
- addressing the ways society at the time enslaved people.
So first let's look at people who had already been enslaved.
The existence of slavery was common-place, to the extent that R. Watkins mentions that no known part of the world was free from taking people as slaves. In fact, even after Islam addressed this topic, for the next 1000 years other civilizations continued to engage in it. Even to this very day, we still see enslavement, whether through sweat-shops driven by capitalist corporations, or economic enslavement through tools like credit.
The word "Slavery" then has many connotations but in modern usage, it is reduced to physical slavery. Whenever someone imagines Slavery, the image of enslaved desert dwellers, chained together with hands and feet with vintage oriental look comes up in the mind, but in reality, it covers more than that.
The problem is equating Islamic slavery concept to Atlantic slavery. Historians have long argued that the White slave trade was unique in its brutality compared to the slavery practised by Islamic Societies.
European orientalist scholars were able to identify Islam as anti-slavery and this caused some of the earlier ones some anxiety. They even ridiculed how "slaves" were treated with dignity and sat with the "common" folk during business hours and engaged in "common" conversations with "common" people. Some European travel writers and colonial rulers (like Cromer) faulted Muslim societies for their "nonhomogeneous" ways concerning "race" and colour .
This was due to the Divine injunctions regarding slaves seen in the examples as follows:
The Prophet (saw) also said: "Whoever kills his slave, we will kill him" [Ahmad] and "Whoever slaps his slave or strikes him, his expiation (kaffara) is to free him." [Sahih Muslim]
So the punishment for killing a 'slave' is to yourself be killed, and to strike them results in their freedom.
Many quote the verse that mentions 'whatever your right hand possesses' but then they do not bring about all the pieces of evidence relating to the topic. For example:
"Fear Allah regarding what your right hand possesses. They are your brothers and Allah has put them under your charge. Feed them with what you eat, clothe them with what you wear and do not impose duties upon them which will make it difficult for them. If you impose duties, then help them…" [Sahih Muslim]
Or this hadith:
"Let not any one of you say 'My slave' (`abdi) and 'my slave-girl' (amati). All of you are the slaves of Allah and all of your women are the slave-girls of Allah. Rather say, 'my boy' (ghulami), 'my girl' (jariyati), 'my young boy' (fataya) and my young girl' (fatati)." [Sahih Muslim].
The word 'slavery' used to refer to a vast spectrum of dramatically different relationships involving labour and control and ambiguity over the word 'wrong,' won't constitute the absolute answer on that. Islamically, it is appropriate and the Islamic economic system works upon that. Under the same standard, the employee working under the manager will by definition be regarded as a slave.