In Bible times, when a man died, his goods and lands were divided between his sons. If he had no sons, his inheritance went to his daughters. If he had no children, the inheritance went to his brothers. If he had no brothers, it went to his father's brothers. If there were no uncles, it went to his nearest male kinsman in his clan (Num. 27:8-11). Children of a concubine might be given gifts and sent away (Gen. 25:6) unless the concubine was serving as a surrogate mother for a wife, such as Bilhah for Rachel and Zilpah for Leah (Gen. 30:3, 9).
Among the sons, the one born first had what was called a birthright. The birthright was the right to inherit a double portion (Deut. 21:17). Thus if there were two sons, the oldest would inherit two-thirds and the youngest one-third. So when Esau sold his birthright for a bowl of bean soup, he gave up the right to one-third of the inheritance from his father (Gen. 25:31-34) If there were twelve sons, the oldest would inherit two-thirteenths and all the others would inherit one-thirteenth. If a father was displeased with a son, he could give the birthright to a younger son. Thus, Jacob passed over Reuben because his slept with his father's concubine (1 Chron. 5:1). Instead, Jacob gave the birthright to Joseph (counting Manasseh and Ephraim as his sons), the first son of his favorite wife Rachel (Gen. 29:30; 30:23-24; 48:5; 1 Chron. 5:2). The law of Moses said that the Israelites were not to do that; they were to give the birthright to the firstborn, even if this son was not born to the favorite wife (Deut. 21:15-17).
Inheritance was considered so important that provision was made for a son to pass his inheritance even if he died without children. This was accomplished through what is called levirate marriage. If a man died without children, his brother (or nearest male relative) was to marry his widow and the first child born was considered the heir of the dead man (Deut. 25:5-6). An example of this is found in the book of Ruth where Boaz marries Ruth to keep the inheritance of Elimelech and his son Mahlon intact (Ruth 4:9-10). But this was a practice for inheritance, not genealogy. The child born to Ruth and Boaz was considered the son of Boaz, not Mahlon (Ruth 4:21; Matt. 1:5).
A widow had rights to her dead husband's property during her life (Ruth 4:3; 2 Kings 8:6). Jesus rebuked the scribes who cheated widows out of their houses (Mark 12:40; Luke 20:47).
This helps understand a couple of stories in the Old Testament. Boaz was not the closest male relative. He offered the closest relative the first right to buy Elimelech's property from Naomi, but said the man would have to marry Ruth as well. The man replied that he could not do so because it would impair his own inheritance (Ruth 4:3-6). This is because he would have to take some of his own wealth that should go on his death to his children and pay that to Naomi. On her death the first child born to Ruth would inherit that property, reducing the amount that would go to his current children.
In the same way, when Judah's first son died, he told his second son to take the wife Tamar and raise up a son for the dead brother. But he realized that the son born would not be considered his and so when he had sex with Tamar, he would waste his seed on the ground. God was displeased with his action and he died (Gen. 38:8-10). Some have reasoned from this that contraception is wrong. But this text is not really about contraception but about inheritance. The second son Oman realized that with his older brother dead, he would get the birthright and with only one other brother, he would get two-thirds of the inheritance. However, if he produced a son for his dead brother, the inheritance would be divided four ways with the child inheriting half, and he would only receive one-fourth. In his greed for the inheritance, he made sure that no son would be born. To be sure, a primitive form of contraception was used, but the real problem was his greed. The contraception was just a means to an end.
There is application in all this to Christians. We are considered children of God and thus heirs (Rom. 8:16-17; Gal. 4:6-7). Both men and women are called sons of God because sons inherit (Gal. 3:26). But even though Christ is called the firstborn (Rom. 8:29; Col. 1:15, 18; Rev. 1:5). But we do no lose anything, for we are all called firstborn (Heb. 12:23; plural in Greek).
Bruce Terry