Understanding the Salvation History
With the election of Israel a single nation in the world was "upgraded" in status from a slave to a free worker, an employee, a mercenary, a servant of God. Indeed, the chief theme in the Old Testament is negotiation: God negotiates with Abraham, He negotiates with Moses, He negotiates with Israel as a whole, because He wants something from them, because they are of use to Him. And for the task that God wants Israel to complete, slaves are inadequate. That is, in order to squeeze some performance out of Israel that could not be elicited from a slave, God had to allow it considerable freedom. In Ludwig von Mises's words:
Primitive man makes no distinction between his property in women, children, and slaves on the one hand and his property in cattle and inanimate things on the other. But as soon as he begins to expect from his slaves services other than such as can also be rendered by draft and pack animals, he is forced to loosen their chains.
He must try to substitute the incentive of self-interest for the incentive of mere fear; he must try to bind the slave to himself by human feelings. ...
The slave becomes intent upon satisfying his master through application and carrying out the tasks entrusted to him; the master becomes intent upon rousing the slave's zeal and loyalty through reasonable treatment. (Human Action, 629)
And Israel knew of its power over God. That's why they always complained (e.g., "All the Israelites grumbled against Moses and Aaron, and the whole assembly said to them, 'If only we had died in Egypt! Or in this desert! Why is the LORD bringing us to this land only to let us fall by the sword? Our wives and children will be taken as plunder. Wouldn't it be better for us to go back to Egypt?'" (Num 14:2-3)) That's why they were stiff-necked: they had the incentives for that kind of behavior, for they knew that God could not throw them away. That's why Moses could argue that
Then the Egyptians will hear about it! By your power you brought these people up from among them. And they will tell the inhabitants of this land about it. They have already heard that you, O LORD, are with these people and that you, O LORD, have been seen face to face, that your cloud stays over them, and that you go before them in a pillar of cloud by day and a pillar of fire by night.
If you put these people to death all at one time, the nations who have heard this report about you will say, "The LORD was not able to bring these people into the land he promised them on oath; so he slaughtered them in the desert." (Num 14:13-16)
For Moses, too, knew that God could not kill His employee. Punish, yes. Kill thousands of them, yes. But not all of them.
Before the election of Israel this was never an issue. God decided one day to wipe out almost the whole of humanity in the Flood (I am assuming the correctness of early Genesis for the sake of argument), and He did. He did not care; men belonged to Him as chattel. What is it to God if a slave is unhappy or if a slave dies? He can create a hundred million more, and it would not cost Him a thing. ("I tell you that out of these stones God can raise up children for Abraham," says Jesus. (Mt 3:9))
Even when God deals with Cain by protecting him from being killed, He does not do this because he expects to make use of Cain. Yes, Cain benefited from God's actions, but he did not cease to be property, because the purpose of God's assistance was to get the Earth to be filled, and that power, namely, to procreate, Cain has in common with irrational animals.
For that reason also in Gen 5 we encounter such perfectly dry accounts as "When Adam had lived 130 years, he had a son in his own likeness, in his own image; and he named him Seth. After Seth was born, Adam lived 800 years and had other sons and daughters. Altogether, Adam lived 930 years, and then he died." (Gen 5:3-5) This "and then he died" is mentioned quite a few times. This is still God's story and not His slaves' story; in fact, slaves have no story. And neither therefore did Adam and Seth and Enosh and the rest of them. Their sole purpose was to fulfill God's first commandment, viz., to be fruitful and multiply. Until Abraham.
Notice also that slavery was limited in Israel, thus the Lord says:
If one of your countrymen becomes poor among you and sells himself to you, do not make him work as a slave. He is to be treated as a hired worker or a temporary resident among you; he is to work for you until the Year of Jubilee. Then he and his children are to be released, and he will go back to his own clan and to the property of his forefathers.
Because the Israelites are my servants, whom I brought out of Egypt, they must not be sold as slaves. Do not rule over them ruthlessly, but fear your God. (Lev 25:39-43)
To be sure, we are treated to all sort of gory details about Israel's ethnically cleansing the nations around it so that they could enter and live in the promised land, as well as the information on all the men they killed and virgins they captured. But such violence was possible because, while Israel was a mercenary, the rest of the world was still enslaved, and so, as property of God, the other nations could be destroyed by Israel without injustice, if God willed it this way.
It is interesting that God found Moses so useful that He did not "smite" him but treated him with extreme patience when Moses was inventing reasons why he should not return to Egypt. Moses was so essential to God's plans that God even showed him a glimpse of His glory and perhaps even (and this is pure speculation) in so doing revealed to him a part of His plan.
A possible objection. When parents give birth to a child, they do not own him as their property; rather, they exercise guardianship rights over him. Why then do I say that God possessed human beings as slaves? What is the difference? The difference is that parents only create the child's body, while God creates both human bodies and souls. Therefore (1) humans belonged to God body and soul, and (2) there was no time after which a person could "leave" God's mastership as he leaves his parents' house and becomes autonomous.
Now <nature, grace, glory> corresponds to <slave, servant, child>. Therefore, even after the Incarnation human beings were not lifted up into the rank of God's children. However, their reward for obeying the Commandments and the promptings of grace has been increased, through Israel, from merely temporal to eternal. Attaining participation in God's inner life is now possible. Just as slaves are not at all on God's mind, good servants of God are far rarer and command His attention. "For many are invited, but few are chosen." (Mt 22:14)
Finally, those who have entered glory are indeed children of God. They have overcome and are warriors who have proved themselves worthy. The have braved the dangers of the world and beat the devil himself into submission. Such saints are apples of God's eyes. It might be objected that the Lord's prayer addresses God as "our Father." But I think that God is our Father insofar as we are actually righteous; but He is not our Father insofar as we are potentially sinners and are not yet confirmed in goodness, that is, we do not yet have the (accidental) grace in which we live become our nature. The prayer emphasizes our hope, confidence, and courage in that God will be our Father 100% in the life to come.
That also solves a particular version of the problem of evil, namely, that if God is our Father, then why isn't He guarding and guiding us through life? The answer is that God is our Lord not Father, at least not yet. We are being "grown" to join the vine-and-branches through charity, and God died on the cross for our potential, but it is only in heaven that we are "deified," no longer property or even useful employees but fully part of God's family.