In the history of Abraham, the existence of slavery, that is, the absolute right of property which one man holds over another, meets us at every turn; and, subsequently, throughout the Scripture, it frequently comes under our notice as a large and important fact in the history and condition of nations.

As in the history of Abraham, we may recognize almost every species of slave that existed in later ages, the fact must  in his time, have been of long standing. Whether it existed before the deluge or not, cannot be said; but the probability is, that it did; for the same causes existed before that event, that produced it within so short a time afterwards. The men who, before the flood, filled the earth with violence and with crime, were not likely to neglect this encroachment upon human rights. The knowledge of the existence of this practice before the flood, would facilitate and hasten its reproduction after that event.

Abraham himself possessed many slaves; indeed, there is no reason to doubt that his encampment was wholly composed of such persons—male slaves with their wives and families; all equally the property of their lord, but becoming such under different circumstances, which practically produced some difference in the estimation in which they were held, if not in the treatment they received from their master.

The first were house-born slaves, that is, slaves born the property of their master, being the children of all the other kinds of slaves previously possessed. We are told that we ought to view these matters in the same light as the ancients and the orientals. We see not the necessity of this. We may view the conduct of men by the light of their age and country—and we may judge leniently of practices respecting which we have ourselves been very slow and very late in coming to a right judgment. But, having now, at last, in the nineteenth century of Christ, come to that right judgment, there is no reason why we should not, and every reason why we should, exercise it in judging of ancient things. So judging, the presence of house-born slaves seems to be the most revolting particular in the whole system. We can understand that a man might forfeit his personal liberty by crime or by misfortune—but that his children and his children’s children should to all generations be involved in the same doom, merely because they are his children, and without any taint derived from him, is most horrible—and seems the most atrocious invention that ever entered the minds of men. Most things of this nature are, however,  worse in principle than they appear to be in practice. The house-born slaves, whose condition seems at the first view the most degraded, are, in fact, the most privileged, trusted and favored. Their services are the lightest and most confidential; they are nearest the person of their master; growing up under his eye, they learn to regard him in some sort as their father; and taking into view the extent of paternal authority in the East, and the respectful distance at which children are kept, the demeanor of the house-born slave towards his master is, in its combinations of deference and attachment, scarcely distinguishable from that of his own children. Except in the utmost extremity of evil fortune, no man will part with a slave of this class. It is counted disgraceful to sell him. And although theoretically this bondage is eternal—it very seldom lasts for two generations. It is very usual for a master to bequeath liberty to all his house-born slaves at his death. He frequently bestows freedom upon some of them in his life-time, if they will accept it, or if he finds an occasion of thereby advancing their welfare. An accomplished and faithful slave often receives the hand of his master’s daughter, and thus becomes a free member of the family. Note: An instance of this occurs in 1Ch_2:34-35—and that too with reference to one who was not, it would seem, a house-born but an acquired slave. “Sheshan had no sons, but daughters; and Sheshan had a servant, an Egyptian, whose name was Jarha. And Sheshan gave his daughter to Jarha his servant to wife.”] Not seldom the master, if childless, adopts a slave of this class for his son, and brings him up as such; or at his death leaves all his possessions to one of them who has won the most of his favor, or whose attachment has been the most tried. In the case of Abraham, we see it is only the house-born slaves that he arms for the pursuit of the five kings; and in the contemplation of dying childless, he clearly indicates the intention of making his house-born slave Eliezer his heir. He had probably acquired many slaves of this sort by inheritance, and a portion were the progeny of these and of his other slaves. 
Some of his slaves, Abraham held by right of purchase. They were “bought with his money.” (Gen_17:12.) There seems, indeed, to have been a regular traffic in the persons of men. We have an instance of this in the case of Joseph. When the unnatural brethren were deliberating upon taking away his life, the approach of a company of travelling merchants on their way to Egypt suggests to them the idea of selling him for a slave. The proposal was made, and the transaction completed, without any apparent emotion of surprise, or any nice inquiries into the right of disposal. Had the dealers been in the habit of paying any heed to circumstances, or to the representations and complaints of those offered to them for sale, they would not have purchased Joseph for a slave. We are not, however, to suppose that Abraham had any concern in acts of this questionable nature. Such slaves passed from hand to hand, and doubtless Abraham’s purchased slaves were acquired not at first hand, but in the market—perhaps in Egypt, which, from the earliest historical time, was a great mart for slaves.

Many of Abraham’s slaves were, however, presented to him. Of these, we know that he received some from the king of Egypt; Hagar may have been one of the number, for she is called “an Egyptian.” Was she so called because she was acquired in that country, or because she was a native Egyptian? If the latter, how did she become a slave in her own country? And how came a native Egyptian to be given or sold to a foreigner like Abraham? `There seems a difficulty in this; and also one still greater in the fact (as appears by the case of Jarha, just noticed) that the Israelites could hold Egyptians as slaves, even in Egypt. As natives of the country in which they were slaves, these could not have been captives taken in war, who formed by far the greater proportion of slaves in all times. In early wars, a captured enemy was regarded as having forfeited his life, and was accordingly put to death—until it was found more advantageous to preserve his life for the sake of his labor, or for the sake of the money that might be obtained from those to whom his  services might be useful. This, which was in the first instance the effect of wars, eventually produced wars; for the captives were thus rendered so profitable, that wars were often made, and aggressive expeditions undertaken, for the sake of the captives and spoil, as is at this day the case in Africa.

Again, the paternal authority in ancient times was such, that the father possessed the most absolute power over the life and condition of his children. It was, and still is in some countries, optional with him from the first, whether the child shall live or not. If it lived, he had a perfect right, under any exigency that might arise, of casting forth, of selling, or even of slaying his child. Many were sold, especially in times of famine, when the parent, being no longer able to find food for them, would consider that he rendered them a kindness by selling them, and all his rights in them, to those able to provide for them. This occurs in our own day. We have with our own eyes beheld parents, in “the straitness of the famine and want of all things,” offering their children for sale in the streets, and asking but the veriest trifle for them.

Then, in countries where there is no legal provision for the poor, a man will often, in time of scarcity, or under some pressing want, sell himself, for the purpose of obtaining food or money. This slavery was sometimes for a limited time, as in the case of Jacob, who served Laban fourteen years for his two daughters—and in that case this condition approaches that of our servants. But it is oftener absolute, as in the case of the Egyptians who sold themselves for bread to their king. Gen_47:23.
Then, again, creditors had the right of seizing the children of a debtor, and himself also, and of selling them in payment of his debts. The children were, indeed, liable to be sold for the debts of the parent even after his death, as we find by the case of the widow who complained to Elisha that, being unable to pay the debts of her deceased husband, the merciless creditor threatened to take her sons for  bondmen. 2Ki_4:1. With this, other cases, in Neh_5:1-5, and Mat_18:25, may be compared.
Men were also enslaved as a punishment for their crimes. But in general, and except in Egypt, where human labor was much in demand for public works, this was confined to cases in which restitution for a wrong might thus be made. In other cases, the punishments of crime were, in old times, generally personal—death, mutilations, tortures, stripes—as is still the case in the East.

We thus see that persons might become slaves even in their own country; and in view of the instances of Egyptians being slaves to foreigners, to which we have referred, it is very possible that the law of Moses aimed at the correction of this sort of grievance, when it forbade that a native Israelite should be sold to a foreigner out of his own country. In his country a stranger might be his master, although in that case his friends, or other Israelites, had the right of redeeming him out of that alien servitude.
From the character of Abraham, as well as from the generally mild tone of Eastern slavery, we must conclude that all his slaves were treated not only with justice and humanity, but with paternal kindness and consideration; and in many cases their being brought into his family must have been a great blessing to them, as the means of bringing them to an acquaintance with God. Living in times when slavery was the usual form of servitude—and knowing that by themselves the power was humanely and conscientiously exercised, even the patriarchs would be slow to perceive the evil principle that lurked in this absolute power of man over man, and would fall into the practice as affording the only mode it which the services they needed could be obtained.