How could it be antislavery if Moses and Aaron were allowed to have their own slaves?
(I wasn't speaking to the ANTI part of your question.)
You know as well as most, that the SLAVERY that appears in most places in the Book is NOT the forced kind, but more of an endentured person, especially in the NT.
Romans 6
1. What shall we say, then? Shall we go on sinning so that grace may increase?
2. By no means! We died to sin; how can we live in it any longer?
3. Or don't you know that all of us who were baptized into Christ Jesus were baptized into his death?
4. We were therefore buried with him through baptism into death in order that, just as Christ was raised from the dead through the glory of the Father, we too may live a new life.
5. If we have been united with him like this in his death, we will certainly also be united with him in his resurrection.
6. For we know that our old self was crucified with him so that the body of sin might be done away with, that we should no longer be slaves to sin--
7. because anyone who has died has been freed from sin.
8. Now if we died with Christ, we believe that we will also live with him.
9. For we know that since Christ was raised from the dead, he cannot die again; death no longer has mastery over him.
10. The death he died, he died to sin once for all; but the life he lives, he lives to God.
11. In the same way, count yourselves dead to sin but alive to God in Christ Jesus.
12. Therefore do not let sin reign in your mortal body so that you obey its evil desires.
13. Do not offer the parts of your body to sin, as instruments of wickedness, but rather offer yourselves to God, as those who have been brought from death to life; and offer the parts of your body to him as instruments of righteousness.
14. For sin shall not be your master, because you are not under law, but under grace.
15. What then? Shall we sin because we are not under law but under grace? By no means!
16. Don't you know that when you offer yourselves to someone to obey him as slaves, you are slaves to the one whom you obey--whether you are slaves to sin, which leads to death, or to obedience, which leads to righteousness?
17. But thanks be to God that, though you used to be slaves to sin, you wholeheartedly obeyed the form of teaching to which you were entrusted.
18. You have been set free from sin and have become slaves to righteousness.
19. I put this in human terms because you are weak in your natural selves. Just as you used to offer the parts of your body in slavery to impurity and to ever-increasing wickedness, so now offer them in slavery to righteousness leading to holiness.
20. When you were slaves to sin, you were free from the control of righteousness.
21. What benefit did you reap at that time from the things you are now ashamed of? Those things result in death!
22. But now that you have been set free from sin and have become slaves to God, the benefit you reap leads to holiness, and the result is eternal life.
23. For the wages of sin is death, but the gift of God is eternal life in Christ Jesus our Lord.
Wages ... payment for work done.