Kitto's Popular Cyclopedia of Biblial Literature
The Old Testament does not contain any word equivalent to this; but the act occurs in various forms. The New Testament has the word often (Romans 8:15; Romans 8:23; Romans 9:4; Galatians 4:5; Ephesians 1:5); but no example of the act occurs. The term signifies the placing as a son of one who is not so by birth.
The practice of adoption had its origin in the desire for male offspring among those who have, in the ordinary course, been denied that blessing, or have been deprived of it by circumstances. This feeling is common to our nature; but its operation is less marked in those countries where the equalizing influences of high civilization lessen the peculiar privileges of the paternal character, and where the security and the well-observed laws by which estates descend and property is transmitted, withdraw one of the principal inducements to the practice. And thus most of the instances in the Bible occur in the patriarchal period. The law of Moses, by settling the relations of families and the rules of descent, and by formally establishing the Levirate law, which in some sort secured a representative posterity even to a man who died without children, appears to have put some check upon this custom. The allusions in the New Testament are mostly to practices of adoption which then existed among the Greeks and Romans, and rather to the latter than to the former; for among the more highly civilized Greeks adoption was less frequent than among the Romans. In the East the practice has always been common, especially among the Semitic races, in whom the love of offspring has at all times been strongly manifested.
It is scarcely necessary to say that adoption was confined to sons. The whole Bible history affords no example of the adoption of a female.
The first instances of adoption which occur in Scripture are less the acts of men than of women, who, being themselves barren, gave their female slaves to their husbands, with the view of adopting the children they might bear. Thus Sarah gave her handmaid Hagar to Abraham; and the son that was born, Ishmael, appears to have been considered as her son as well as Abraham's, until Isaac was born. In like manner Rachel, having no children, gave her handmaid Bilhah to her husband, who had by her Dan and Naphtali (Genesis 30:5-9); on which his other wife, Leah, although she had sons of her own, yet fearing that she had left off bearing, claimed the right of giving her handmaid Zilpah to Jacob, that she might thus increase their number; and by this means she had Gad and Asher (Genesis 30:9-13). In this way the greatest possible approximation to a natural relation was produced. The child was the son of the husband, and, the mother being the property of the wife, the progeny must be her property also; and the act of more particular appropriation seems to have been that, at the time of birth, the handmaid brought forth her child 'upon the knees of the adoptive mother' (Genesis 30:3). A curious fact is elicited by the peculiar circumstances in Sarah's case, which were almost the only circumstances that could have arisen to try the question, whether a mistress retained her power, as such, over a female slave whom she had thus vicariously employed, and over the progeny of that slave, even though by her own husband. The answer is given, rather startlingly, in the affirmative in the words of Sarah, who, when the birth of Isaac had wholly changed her feelings and position, and when she was exasperated by the offensive conduct of Hagar and her son, addressed her husband thus, 'Cast forth this bond-woman and her son; for the son of this bondwoman shall not be heir with my son, even with Isaac' (Genesis 21:10).
A previous instance of adoption in the history of Abraham, when as yet he had no children, appears to be discoverable in his saying, 'One born in my house is mine heir.' This unquestionably denotes a house-born slave, as distinguished from one bought with money. Abraham had several such; and the one to whom he is supposed here to refer is his faithful and devoted steward Eliezer. This, therefore, is a case in which a slave was adopted as a son—a practice still very common in the East. A boy is often purchased young, adopted by his master, brought up in his faith, and educated as his son; or if the owner has a daughter, he adopts him through a marriage with that daughter, and the family which springs from this union is counted as descended from him. But house-born slaves are usually preferred, as these have never had any home but their master's house, are considered members of his family, and are generally the most faithful of his adherents. This practice of slave adoption was very common among the Romans; and, as such, is more than once referred to by St. Paul (Romans 8:15; Galatians 4:5-6), the transition from the condition of a slave to that of a son, and the privilege of applying the tender name of 'Father' to the former 'Master,' affording a beautiful illustration of the change which takes place from the bondage of the law to the freedom and privileges of the Christian state.
As in most cases the adopted son was to be considered dead to the family from which he sprung, the separation of natural ties and connections was avoided by this preference of slaves, who were mostly foreigners or of foreign descent. For the same reason the Chinese make their adoptions from children in the hospitals, who have been abandoned by their parents. The Tartars are the only people we know who prefer to adopt their near relatives—nephews or cousins, or, failing them, a Tartar of their own banner. The only Scriptural example of this kind is that in which Jacob adopted his own grandsons Ephraim and Manasseh to be counted as his sons (Genesis 48:6). The object of this remarkable adoption was, that whereas Joseph himself could only have one share of his father's heritage along with his brothers, the adoption of his two sons enabled Jacob, through them, to bestow two portions upon his favorite son. The adoption of Moses by Pharaoh's daughter (Exodus 2:1-10) is an incident rather than a practice; but it recalls what has just been stated respecting the adoption of outcast children by the Chinese. In 1 Chronicles 2:34, etc. there is an instance recorded of a daughter being married to a free slave, and the children being counted as those of the woman's father. The same chapter gives another instance. Machir (grandson of Joseph) gives his daughter in marriage to Hezron, of the tribe of Judah. She gave birth to Segub, who was the father of Jair. Jair possessed twenty-three cities in the land of Gilead, which came to him in right of his grandmother, the daughter of Machir; and he acquired other towns in the same quarter, which made up his possessions to three-score towns or villages (1 Chronicles 2:21-24; Joshua 13:30; 1 Kings 4:13). Now this Jair, though of the tribe of Judah by his grandfather, is, in Numbers 32:41, counted as of Manasseh, for the obvious reason which the comparison of these texts suggests, that, through his grandmother, he inherited the property, and was the lineal representative of Machir, the son of Manasseh.
Kitto, John, ed. Entry for 'Adoption'. "Kitto's Popular Cyclopedia of Biblial Literature". https://www.studylight.org/encyclopedias/eng/kbe/a/adoption.html.