“A slave is a person who does not own his own labor. He is purchased not to be abused and to have his mobility restricted. He is purchased for his labor.”
Generally speaking, I own my own labor till I sell or trade it to another. After that, all else being equal, I am contractually obligated to provide the labor and the other is contractually obligated to compensate me.
I am not purchased for my labor...my labor is purchased from me.
I think he was referring to the government owning your labor.
For many people, the government gets a greater percentage of the earnings from their labors than they do.
On tax day you are forced to sign an oath to the government or go to prison. The government owns you and your labor.