The Law of the Unloved Firstborn: Deuteronomy 21:15-17
Introduction: Law vs. Feelings
We live in an age that has enthroned the wavering, fickle, and utterly untrustworthy god of human feelings. Our culture's highest law, its ultimate standard of righteousness, is "how I feel about it." This is the rotten foundation upon which our entire ethical superstructure is built, and it is why the whole thing is coming down around our ears. We are told to follow our hearts, to be true to ourselves, and to let our passions be our guide. But the prophet Jeremiah tells us that the heart is deceitful above all things, and desperately sick (Jer. 17:9). To follow your heart is to follow a blind, raving lunatic off a cliff.
God's law, in stark contrast, is objective. It is outside of us. It does not care about our feelings, our preferences, or our personal affections. It establishes a standard of righteousness that is as fixed and immovable as God Himself. This is a tremendous mercy. It means that justice is not subject to the whims of a father's favoritism or a judge's bad mood. It means there is a real standard of right and wrong that we can appeal to, a standard that protects the weak from the strong and the unloved from the whims of the loved.
In this peculiar little case law, tucked away in Deuteronomy, we find this principle applied with surgical precision to a messy, painful, and very real family situation. The law anticipates the fallen realities of a polygamous household, not to endorse polygamy, but to regulate it with justice. The Old Testament never presents polygamy as the ideal; Genesis 2 sets the pattern of one man and one woman. But when the ideal is broken, as it so often is, God in His wisdom provides laws to mitigate the damage and ensure that sin does not have the last word. This law is a direct assault on the tyranny of subjective feelings and a glorious defense of objective, covenantal duty. It is a guardrail for the heart, forcing it to act in righteousness, regardless of how it feels.
We see this precise scenario play out in the life of Jacob. He loved Rachel, but he was unloved toward Leah. And yet, it was through Leah, the unloved wife, that the line of Judah, and ultimately the Messiah, would come. God's sovereign purposes are not thwarted by our tangled affections. His law cuts through the mess and establishes His righteous order, and in this, we see a beautiful picture of the gospel.
The Text
"If a man has two wives, the one loved and the other unloved, and both the loved and the unloved have borne him sons, if the firstborn son belongs to the unloved, then it shall be in the day he wills what he has to his sons, he cannot make the son of the loved the firstborn before the son of the unloved, who is the firstborn. But he shall recognize the firstborn, the son of the unloved, by giving him a double portion of all that he has, for he is the first of his vigor; the legal judgment for the firstborn belongs to him."
(Deuteronomy 21:15-17 LSB)
The Messy Reality (v. 15)
The law begins by acknowledging a situation that is far from God's creational ideal, but which was a reality in the ancient world.
"If a man has two wives, the one loved and the other unloved, and both the loved and the unloved have borne him sons, if the firstborn son belongs to the unloved..." (Deuteronomy 21:15)
The law is not commanding polygamy here; it is regulating it. This is what we call case law. It takes a specific situation, an "if," and provides the righteous response, the "then." The existence of laws regulating slavery or polygamy in the Old Testament is not a divine thumbs-up for those institutions. Rather, it is God condescending to the hardness of men's hearts to restrain evil and establish a floor of justice in a fallen world. Left to ourselves, we would make a far greater hash of things.
The scenario is painfully direct: one wife is loved, and the other is "unloved." The Hebrew word here can also mean "hated." This is not necessarily the seething, malicious hatred our culture thinks of, but rather a comparative term. It means she is neglected, passed over, not the object of the husband's primary affection and delight. This was precisely the situation with Jacob, Leah, and Rachel. Genesis 29:31 says, "When the LORD saw that Leah was unloved, He opened her womb." God sees the unloved. He is the defender of the slighted, the advocate for the underdog.
The situation is complicated by the fact that the firstborn son, the heir, belongs to this unloved wife. You can feel the domestic tension. The husband's heart is with his favored wife and her children. His natural inclination, his feeling, would be to treat her son as the heir, to give him the privileges and the inheritance that belong to the firstborn. The stage is set for a gross injustice, driven entirely by the father's subjective affections.
The Prohibition of Favoritism (v. 16)
God's law steps directly into this emotional minefield and lays down a firm, unyielding prohibition.
"...then it shall be in the day he wills what he has to his sons, he cannot make the son of the loved the firstborn before the son of the unloved, who is the firstborn." (Deuteronomy 21:16 LSB)
Here is the central command. The father's feelings are declared legally irrelevant. The day he draws up his will, the day he distributes his inheritance, he is forbidden from rewriting history. He cannot let his personal preference overturn the objective fact of birth order. The son of the loved wife cannot be treated as the firstborn. Why? Because he is not the firstborn.
This is a profound statement about the nature of truth and justice. Justice is not about validating our feelings; it is about conforming to reality. The reality was that the son of the unloved wife was, in fact, the firstborn. To deny this would be to act on a lie, and God's law never sanctions lies, especially when they are used to disinherit the vulnerable. This law protects the son from the emotional fallout of his parents' dysfunctional relationship. His standing before the law is not dependent on his father's affection for his mother. It is an objective, God-given status.
This cuts right across the grain of our modern therapeutic culture. We believe our affections are self-validating. If we feel it, it must be true and right. God says otherwise. He says your affections can be disordered, sinful, and unjust, and when they are, they must be brought into submission to His righteous standard. You are commanded to do what is right, even if you do not feel like it. Over time, faithful obedience has a way of reordering the affections, but the obedience must come first.
The Mandate of Justice (v. 17)
The law does not stop with a negative prohibition; it issues a positive command, defining exactly what righteous action looks like.
"But he shall recognize the firstborn, the son of the unloved, by giving him a double portion of all that he has, for he is the first of his vigor; the legal judgment for the firstborn belongs to him." (Deuteronomy 21:17 LSB)
The father must "recognize" or "acknowledge" the firstborn. He must publicly and legally affirm the reality of his son's status. And this recognition is not just a matter of words; it has teeth. It involves giving him a "double portion." This was the right of the firstborn. If there were, say, three sons, the inheritance would be divided into four parts. The firstborn would receive two parts, and the other two sons would each receive one. This was not to show that he was twice as valuable, but to equip him for his greater responsibility as the new head of the clan, responsible for caring for his mother, his unmarried sisters, and the general welfare of the family.
The law provides two reasons for this. First, "he is the first of his vigor." This points to the objective, biological reality. He is the firstfruit of the father's strength. This is a fact of history, and it cannot be changed by feelings. Second, "the legal judgment for the firstborn belongs to him." The right of the firstborn is his. It is a legal right, established by God, not a gift to be given or withheld based on the father's emotional weather report. The law protects this right from being stolen by favoritism.
The Firstborn and the Gospel
Like all of God's law, this specific case points us beyond itself to greater realities. It points us to the gospel and to the character of God our Father.
First, we see that God's covenant love is not based on our loveliness. In this story, we are all the children of the unloved wife. By our sin, we have made ourselves unlovely and undesirable. We were alienated, hostile in mind, engaged in evil deeds (Col. 1:21). There was nothing in us to attract the Father's favor. We were the children of wrath, just like the rest (Eph. 2:3). If God operated on the basis of feelings or our inherent attractiveness, we would all be disinherited.
But God, in His glorious grace, operates on the basis of His covenant promise and His sovereign choice. He sets His love upon us not because we are lovely, but to make us lovely. His love is not a response to our goodness; it is the cause of it.
Second, this law points us to the true Firstborn, Jesus Christ. Jesus is the Firstborn over all creation (Col. 1:15) and the firstborn from the dead (Col. 1:18). He is the beloved Son, with whom the Father is well pleased. And yet, for our sakes, He was treated as the son of the unloved wife. On the cross, He was hated, despised, and rejected. He cried out, "My God, my God, why have you forsaken me?" He was disinherited so that we, the unloved, could be brought into the family and receive the inheritance.
And what is that inheritance? It is a double portion, and more. Through faith in Him, we are adopted as sons and daughters. We become co-heirs with Christ (Rom. 8:17). He is the firstborn among many brethren. God the Father, with perfect justice, recognizes the rights of His Firstborn, Jesus, by raising Him from the dead and seating Him at His right hand. And in His grace, He shares that glorious inheritance with us. He gives us the rights that belong to the beloved Son, even though we were children of the unloved.
This is the great exchange of the gospel. Our unloved status was placed on Christ, and His beloved status is granted to us. God's law is satisfied, His justice is upheld, and His grace is magnified. He does not play favorites. He does not operate on fickle affections. He operates on the basis of His own righteous character and His unbreakable covenant promises, secured by the blood of His Son. Therefore, let us put away the childish and tyrannical god of our feelings, and worship the one true God, whose law is righteous and whose grace is a rock.