The Bible’s sacrificial theology mandates that the firstfruits of reproduction—whether of plants, animals, or humans—be sacrificed to Yahweh.
“Consecrate every firstborn for me [Yahweh]. The first birth of every womb of the children of Israel, of a human and of an animal, is mine!” (Ex 13:2)
This divine decree must be understood in the context of the Passover narrative. In other words, biblical scribes accredited the origin of sacrificing all firstborn sons to Yahweh to the Passover/Exodus. Its origins, however, most likely lie elsewhere.
Immediately following the Passover narrative, the verse below, which comes from the Elohist, explains this sacrificial theology of the firstborns in the form of commemorative ritual:
And it was when Pharaoh hardened against letting us go, and Yahweh killed every firstborn in the land of Egypt, from firstborn of a human to firstborn of an animal, that on account of this I am sacrificing to Yahweh every first birth of a womb—the males—and I shall redeem every firstborn of my sons. (13:15)
An attentive reader of the Passover narrative, especially P’s version (#109), will notice that the decree to kill all firstborns falls upon all firstborns in the land of Egypt—both those of the Egyptians and the Israelites. However, the firstborns of the Israelites are redeemed, that is a ritual substitution is offered up to Yahweh instead of the male firstborns, namely the pascal lamb (12:12-13). Later on in the Priestly source we are informed that the tribe of the Levites themselves become the sacrificial ransom for all Israelite firstborns.
And Yahweh spoke to Moses, saying: “And I, behold, I have taken the Levites from among the children of Israel in place of every firstborn, the first birth of the womb from the children of Israel. And the Levites shall be mine, because every firstborn is mine! In the day that I struck every firstborn in the land of Egypt, I consecrated every firstborn in Israel to me, from human to animal. They shall be mine. I am Yahweh! (Num 3:11-13).
Thus instead of all male firstborns belonging to Yahweh, the Levites redeem them and it is thus the Levites who belong to Yahweh. This is not only a sacrificial theology of substitution, but it also accords the Levites, like consecrated sacrificial animals, as the “holy ones” of Yahweh.
Yet Exodus 22:28 does not stipulate a ritual substitution: the text has Yahweh pronounce, “You shall give me the firstborn of your sons”—period. Furthermore, the following verse makes no mention of ritual substitution, and rather stipulates that the firstborn of ox and sheep must be given over to Yahweh as sacrifice on the eighth day. We are reminded of the bizarre incident in Exodus 4:22-26, where Yahweh pronounces to Egypt that Israel is Yahweh’s firstborn, and that he plans to kill Egypt’s firstborns. Then, however, the narrative switches, perhaps due to the insertion of different source material, to a story in which Yahweh threatens to kill “him”—Moses’ firstborn?—but this is averted due to his circumcision, which according to P is a ritual performed on the eighth day (see #28). So there is textual evidence to suggest that the rite of circumcision might also have been envisioned as a blood ritual, like that of the pascal lamb, which redeemed Israel’s firstborn males from Yahweh. Along similar grounds is the Aqedah, or the sacrifice of Isaac (Gen 22): Abraham’s firstborn son is redeemed from being sacrificed to Yahweh by a fortuitous ram which functions as a sacrificial substitution.
All of these narratives of ritual substitutions whereby a firstborn male is redeemed from being sacrificed to Yahweh raises the hotly debated question as to whether or not human sacrifice was practiced at some early stage in the history of the cult. This inquiry becomes more intriguing when we take into account other biblical passages that speak of child sacrifice. Michah 6:6-8, Jeremiah 7:31, 19:5, 32:35, and Ezekiel 20:18-31 all mention the sacrifice of firstborns in polemical contexts which vehemently condemn such practices—suggestion, therefore, that it was indeed practiced!
Other poignant evidence includes the narratives of Jephthah who sacrifices his daughter to Yahweh (Judg 11:29-40), king Ahaz who sacrifices his son to Yahweh (2 Kgs 16:3), and the narrative of 2 Kgs 3:26-27, where arrayed in battle formation against the Israelites, the Moabites perform a firstborn male sacrifice to their god, Chemosh, which Yahweh acknowledges—thus our biblical writer contends—as a sacrificial ritual that is effectively favorable toward the Moabites’ victory, and therefore orders the Israelites to retreat! In other words, the biblical authors understood such sacrifices as so powerful that not even Yahweh could have changed the outcome of the battle now! Through this sacrifice, the Moabites have secured their victory! This does not necessarily have to be an historical event. It could just as easily be a powerful theological narrative explaining why the Israelites lost this particular battle.
In conclusion, the biblical record itself (and one should add the archaeological evidence as well) strongly suggests that firstborn sacrifices were intermittently practiced in Israel, and not surprisingly condoned by various biblical authors. At the very least this certainly brings validity to the question of whether or not an early form of the cult of Yahweh practiced firstborn male sacrifices, which were then reinterpreted with respect to the theology of redemption or substitution, either through the Passover narrative, through the consecration of the Levites as Yahweh’s, through the blood rite of circumcision, or ultimately through the sacrificial substitution of Yahweh’s own firstborn according to later Christian theologians, Jesus!