It is not just about the animal sacrifice it goes deeper than that. We (I) must follow through on our (my) commitment to G-d and following HIS mitzvahs.
“Every tenth animal born must be offered up as a sacrifice, its meat eaten by the owner and his family. The owner is not allowed to substitute another animal for the tithed animal, but if he nevertheless does, both animals must be treated as having been tithed.
[G‑d instructed Moses to tell the Jewish people,] “If [the tithed animal’s owner] does substitute it, then both it and its replacement will be holy.” Leviticus 27:33
Sanctifying an animal is a good thing. Why, then, should the Torah forbid the owner to substitute another animal for the original, tithed one, if by doing so both animals become sanctified?
When someone tithed his animals, he was lifted out of his mundane world and drawn into the holy process of having to take the animal to Jerusalem and eat it there with his family. This gave him the opportunity to renew his religious inspiration at the holy Temple. The Torah wants the owner to take advantage of this opportunity and see it through – not to focus on some other, unconsecrated animal.
Normally, we should follow this advice, as well: If we are involved in some holy pursuit, we should stay focused on it. We should not sacrifice our spiritual momentum for some material diversion.
However, when other people are in spiritual danger, we must overlook this prohibition in order to reach out to them. In such cases, the Torah assures us that G‑d will protect us. Both we and those whom we elevate to holiness will indeed remain holy.1 Likutei Sichot, vol. 26, pp. 90–92.