Weird laws require patience and tenacity because they are often clarified by other laws and stories in the Bible.
For example, “the firstborn of your sons you shall give to me” (Exodus 22:29). What? Why? We find a bit more clarity a few chapters later. “All the firstborn of your sons you shall redeem. None shall appear before me empty-handed” (Ex 34:20). OK, so this law is about redeeming the firstborn. But where did this idea come from? Eden.
God in his mercy redeemed his firstborn human son with the sacrifice of an animal (Genesis 3:21). In doing so, God rescued humanity from total ruin and restored their purpose for living even in their fallen state. Redeeming “the firstborn son” is about consecrating human participation in God’s mission. Adam, God’s firstborn human son, represented all his future offspring.
Redeeming “the firstborn son” was dramatically displayed when God told Abraham to “take your son, your only son … and offer him as a burnt offering” (Gen 22:2). This is not a demand for human sacrifice to appease an angry God. It is about redeeming, consecrating, dedicating the firstborn son to God’s mission. Burnt offerings could symbolize either atonement for sin or full surrender to God. Offering Isaac was the clearly the latter—and Abraham knew it. He even called it “worship” (Gen 22:5).
Notice what Abraham told Isaac (who was probably 36-37 years old at the time): “God himself will provide the lamb for the burnt offering” (Gen 22:8a). Abraham trusts that a lamb will show up or there will be a physical resurrection from the dead. “He considered that God was able even to raise him from the dead, from which, figuratively speaking, he did receive him back” (Hebrews 11:19). Either way, Abraham’s promise to “return” (Gen 22:5) implies that he and Isaac will both come down Mount Moriah alive—which they did. God never intended Abraham to kill Isaac. This was a huge test about surrendering, consecrating, redeeming the firstborn son to God’s mission!
We see this again in Egypt when, once again, God consecrates Abraham’s collective firstborn son. “Israel is my firstborn son … Let my son go that he may serve me” (Ex 4:22-23). Israel, God’s collective firstborn son was redeemed so that they could join God’s mission as a kingdom of priests (Ex 19:5-6).
The law of redeeming the firstborn son was ultimately fulfilled when God offered his only begotten Son, “the firstborn among many brothers” (Romans 8:29). In his triumph over sin and death, once for all, Jesus redeems “the church of the firstborn” as a kingdom of priests who participate in God’s mission now and forevermore (Hebrews 12:23).