Exodus 21:21~
“However, if he survives for one or two days, he is not to be avenged, because he is someone bought with his owner’s money.”

From a modern perspective, it makes no sense that the law God handed down to the Israelites through the hand of Moses would regulate slavery rather than abolish it.
After all, hadn’t God just finished a series of spectacular miracles, some at a great cost to human life, with the purpose of freeing them from slavery?
Although that was part of the reason, the main reason God had freed them was to fulfill the promises he had made to Abraham, their ancestor, (Exo. 2:23-25).
The readings from the last two weeks have highlighted the lack of faith the Israelites demonstrated as a whole during the exodus process.
Therefor it is not surprising that a practice common to their times, unfair as it was, would be engrained into their culture; similar to the practice of having more than one wife, which most people in modern Western civilization find objectionable.
God’s purpose never was for slavery to exist, for 1,500 years later Peter arrived at the correct conclusion when he stated: “Now I truly understand that God is not partial, but in every nation the man who fears him and does what is right is acceptable to him,” (Acts 10:34,35).
It would take a very long time to adjust the erroneous thinking of the people of ancient Israel, and most Jews never accepted the new law as prescribed by Christ (Matt. 22:37-40).
In the mean time, God did set forth a set of rules to regulate forced labor.
The Hebrew word e′vedh can mean slave or servant, depending on the context,(Insight on the Scriptures, volume 2).
Hebrews sold into slavery were freed in the seventh year of their servitude, or in the year of the Jubilee, which occurred every 50 years, depending on which came first, and their master had to give them a parting gift for them to start a new life (Exo. 21:2; Deut. 15:13-15).
Female Hebrew slaves were to either become concubines to their masters or legal wives to their sons with all the inheritance rights therein, otherwise they were to be set free. They could not be sold to foreigners (Exo. 21:7-11).
Adult human trafficking of others was illegal and punishable by death (Exo. 21:16).
With that in mind, I will return to the text I cited at the beginning.
Did the law give less value to the life of a slave than to the life of a free person?
If a master injured his/her slave with a non-lethal instrument and the person took more than two days to die, that would indicate the master did not have murder as an intention.
Furthermore, the master would be at an economic loss if the slave did die.
That is why the law protected the master from being avenged if the slave died under these circumstances.
However, if the slave was maimed, he was to be set free (Exo. 21:26,27).
If the slave did die within two days, the master was to be put to death without fail, (Lev. 24:17).
It is not my intention to justify slavery under Mosaic Law. I believe the law came from Jehovah and it was applicable to that culture and time. If they heeded God’s law, their community would benefit and behave more justly than other nations were behaving at that particular point in time.
After all, Jehovah’s wisdom is unquestionable, having “made out of one man every nation of men to dwell on the entire surface of the earth, and he decreed the appointed times and the set limits of where men would dwell, so that they would seek God,” (Acts 17:26).