The Talmud entertains the possibility that the firstborn offering should be compared to, and derive its laws, from a sin offering. Yet Rashi does not even mention this possibility. A possible homiletic interpretation is that the firstborn offering alludes to the Jewish people, who are G-d’s “firstborn” children. The firstborn animal specifically alludes to the animal soul and tendency within the Jew. In the world of straightforward interpretation that Rashi practices, when reality conforms to its most basic expectations, even the animal soul of a Jew is not associated with sin. Instead, the firstborn is compared to the peace offering, because the role of the Jew is to bring peace to the world and reconcile the “animal” self with the G-dly reality.
Rashi does, however, mention the possibility of comparing the firstborn to the thanksgiving offering. This offering is made when a person experiences a miraculous salvation. In spiritual terms, this alludes to the soul needing a miraculous display of self-sacrifice and faith to resist the temptations of sin. Maybe the soul, the “firstborn,” only avoids sin because of a “thanksgiving offering,” because of a heroic measure of self sacrifice? Rashi denies this as well, for a Jew to resist sin is the most natural thing in the world, Rashi implies. We do not require miracles to be connected to G-d, it is in our very nature.
