What is the biblical basis for thinking God established the principle of birthright and inheritance What is the biblical basis for thinking God established the principle of birthright and inheritance and that He has sovereign control over who He elects
Was God himself the author of this teaching or not?
Although birthright privileges for the firstborn son are mentioned in the Bible at the time of Isaac’s death (circa 1886 B.C.), it was not established in Mosaic Law for another 440 years. Even secular sources acknowledge that the custom of passing on rights and privileges to the eldest son “was sufficiently common in the Middle East for the passage [about Esau and Jacob] to seem plausible to the people living there prior to the Roman Empire.”
See Wikipedia’s article on Primogeniture.
The first mention of birthright and inheritance in the Bible is in Genesis chapter 25. Abraham’s son Isaac became father to twin boys (Esau and Jacob). The firstborn son had the right to inherit a double portion because “he is the beginning of his [father’s] strength; the right of the firstborn is his” (Deuteronomy 21:17).  The birthright (bekorah) has to do with both position and inheritance. By birthright, the firstborn son inherited the leadership of the family and the judicial authority of his father.  The father would pronounce a blessing which was considered to be the formal act of acknowledging the firstborn as the principal heir.
Yet, even before the twins were born, the Lord predicted that the older (Esau) would serve the younger (Jacob) (Genesis 25:23).  There are several instances where God’s sovereign will decreed that the firstborn son would not always be the son to inherit.  God cursed Cain, the first son born to Adam and Eve, and blessed Seth, the third son.  Through Seth came Noah, then Shem (who was not the oldest son) and on to Abraham and Isaac (who was not the oldest son), then to Jacob. God changed Jacob’s name to Israel (Genesis 32:28), and he became the father of the 12 tribes of Israel.
Then, in Exodus 4:23 God calls Israel “my firstborn son”. This goes beyond any human notion of the rights and privileges of the firstborn son but speaks of God’s divine will. God also declared Jesus to be his Son (Matthew 3:17), who is described as “the firstborn of the dead, and the ruler of kings on earth” (Revelation 1:5). There is a spiritual application to this issue of firstborn and inheritance.
What is the biblical basis for thinking God established the principle of birthright and inheritance and that He has sovereign control over who He elects
As this question is not concerned with establishing a ‘secular’ answer about the origins of the idea of birth-right (which includes inheritance) I can breathe a sigh of relief and concentrate on collating various Old Testament scriptures that give information on where human and divine views digress. Therein lies the answer to the question, as to whether or not God was the origin of a concept like inheritance.
I suggest that, from the Bible texts I have studied, it can be said that God’s concept of ‘inheritance’ differs radically from human concepts at some critically important points.  Take Psalm 2, for instance. This is a prophetic statement about the Lord God and his Anointed One. Without offering any interpretations, I simply point out that verse 8 has God invite his Son to “Ask of me, and I will make the nations your inheritance, the ends of the earth your possession.” This is where the inherited rule of the Lord’s Anointed becomes the rule of God himself, for to submit to the rule of the Anointed is to “Serve the LORD” God (vs. 11).
Working backwards now, from the greater to the lesser, Bible texts show where God breaks through into what humans considered to be the right of the first-born and his (and it’s usually a ‘his’) inheritance. God keeps asserting his sovereign right to stop humans doing what they would choose to do regarding this birth-right principle.
You have already mentioned examples of this, including Abraham’s miracle child, Isaac, and the twins, Esau and Jacob. The youngest son of Jacob was chosen by God as ‘over’ his 11 brothers. God sent dreams to the lad, Joseph, foretelling this in symbolic imagery; decades later, it came to pass, even his aged father realising it. Jacob blessed Joseph’s second-born son above the first-born son, putting Ephraim ahead of Manasseh. Jacob did not bless his firstborn, Reuben, but said he would no longer excel, then pronounced Joseph ‘prince among his brothers’ (Genesis chapter 48 to 49:1-26).
The daughters of Zelophehad were chosen to inherit (when they stood up and made a legal case for it) due to their father having no sons. Numbers ch. 27 &amp; 36:1-12. Deuteronomy 21:15-17 details the rights of the firstborn (not always the first-born son – a first-born daughter with no brothers could inherit, due to the precedent of Zelophehad’s daughters.)
The youngest son of Jesse was chosen by God as king ‘over’ his many brothers and the nation (1 Samuel 16:1-13). No doubt there are lots of other cases; this is just a sample to show that God’s choosing is not determined by human customs, or even laws. Perhaps that’s because God’s law states that all humans have inherited sin from our original, earthly father, and that “the wages of sin is death” (Romans 5:12 &amp; 6:23). That’s the horrible inheritance we all get and which we need to face up to. Any earthly inheritance is just so much of a soon-to-be rust-bucket heaped full of moth-eaten fabric.
But if God should call us his ‘sons’, adopting us into his heavenly family (Romans chapter 8), then our inheritance is beyond our wildest dreams, kept in heaven for us. Nor is such an inheritance due to any merit or standing on our part, but a freely bestowed gift of grace. Though we be the first-born son of an earthly king or the poorest girl in the gutter, humanly speaking, God elevates those he chooses.
This, to me, indicates that while there may be something of the divine principle of sonship and inheritance in human primogeniture laws, human laws are (as so often is the case) too rigid and short-sighted to grasp the spiritual principles that ought to be their basis.