When did the laws giving special status to the firstborns take effect? Did these laws apply in the desert, or did they take effect only after the Children of Israel entered the land of Israel?
The Gemara on today’s daf brings a difference of opinion regarding this question. Rabbi Yoḥanan notes that the passage in Sefer Shemot (13:2) clearly sets out a requirement to sanctify the firstborn of both humans and animals and concludes that the laws of bekhor applied in the desert. Reish Lakish argues that the continuation of that section in Sefer Shemot teaches that only when the Children of Israel are brought to the Land of Canaan will these laws be applied (see 13:11-12).
In his commentary on the Torah (Shemot 13:11), the Ramban explains that according to Reish Lakish the Torah’s first pronouncement that the firstborn are sanctified applied specifically to the firstborn who were alive at the time of the Exodus. In celebration of the fact that they were saved while the Egyptian firstborn were all killed in the final plague, the Israelite firstborn became sanctified. Nevertheless, the requirement to confer this holiness on future generations did not come into effect until after the journey in the desert was completed.
Rabbi Yoḥanan challenges Reish Lakish’s ruling based on a baraita that states that prior to the erection of the Tabernacle, the sacrificial service in the desert was performed on bamot – private altars – by the firstborn. Reish Lakish responds by arguing that this refers only to the firstborn who were already alive at the time of the Exodus.
The statement that the sacrificial service in the desert was performed by the firstborn is based on a passage in Sefer Shemot (24:5) that describes how in conjunction with the giving of the Torah on Mount Sinai there were a group of “young men” who brought sacrifices (see a discussion of this story in Massekhet Zevaḥim daf 115 ).