Our Gemara on Amud Beis discusses the interesting halacha of Temurah. It is forbidden to exchange an animal dedicated and set aside for a sacrifice with another animal, even if it is superior. Furthermore, if one attempts this exchange, both the newly designated animal and the prior consecrated animal are now sanctified. They both must be used for a sacrifice. As the verse states (Vayikra 27:10), “One may not exchange or substitute another for it, either good for bad, or bad for good; if one does substitute one animal for another, the thing vowed and its substitute shall both be holy.”

We have a tradition that since creation it was always the firstborn who were set aside for priestly duties. As a result of the sin of the Golden Calf, and as a reward to the Levites who did not sin, the privilege was transferred from the firstborn and given to the Levites (Bamidbar Rabbah 4:8). Some raise a question. If there is a principle that an animal that is consecrated cannot be exchanged, and if it is exchanged both the original and the new sacrifice remain and become consecrated, how did the firstborn lose their privilege?

Sefas Emes (Bamidbar 20:4) answers that indeed the firstborn did not totally lose their privilege. It is more that the Levites became an addition and extension. He compares their service to an act done in partnership where one begins and the other finishes, and both are considered participants.

I find this difficult to understand because for all intents and purposes, a firstborn may not perform service in the Temple while a Levite can. However, this is easier to understand in light of those who have a tradition that in future messianic times the privilege of service will be returned to the firstborn. (For example, see Ohr Hachaim, Bereishis 49:28.)

However, Divrei Dovid (on Rashi Bamidbar 8:17) makes a different point. He says, indeed, the firstborn did lose their privilege utterly. He compares this to the difference between a consecrated sacrificial animal that then develops a blemish, which still retains aspects of holiness, versus a firstborn animal that develops a blemish and is completely released for profane non-holy purposes. What is the reason for this distinction? It has to do with the process of how they become holy. Normally an object or animal is consecrated verbally; it is declared and therefore designated for holiness. Once that occurs, there is a state that cannot be fully reversed. On the other hand, the firstborn became consecrated in a de facto manner. The firstborn were, in a manner of speaking, a debt due to God because He saved the firstborn. This is why the verse states in Bamidbar (3:13): “For every such first-born is Mine: at the time that I smote every [male] first-born in the land of Egypt, I consecrated every first-born in Israel, human and animal, to Myself, to be Mine, GOD’s.” The firstborns, unlike regular sacrificial offerings, are automatically sanctified at birth. Therefore, because of this dynamic, there is also a leniency. Just as their status is automatic and due to a particular debt, they can be summarily released from the status should they be disqualified. This is why the firstborn animal with a blemish is completely released, and also why the firstborn humans, upon sinning with the Golden Calf (their blemish), lose their status completely.

There is a deeper lesson as well. Easy come, easy go. If somebody has a gift that they did not earn, be it intelligence or strength, they could lose it as easily as they got it. On the other hand, something that they worked for—in other words, something they declared and mindfully sanctified—never completely loses its status.