they, definitionally, reject Christ's sacrifice

First, you mean rabbinical Jews, because a Lifeway survey estimated there are a million Messianic (Christian) Jews.

Second, I ask people for proof that some congregational rabbi or rabbinical organization teaches, as a tenet of Judaism, that Jesus's sacrifice is rejected. They don't actually do it because they're too scared, they leave the rejection to folk religion and to antimissionaries but they don't make it a tenet of rabbinical Judaism because they know what would happen if they did. So I decline the statement that rabbinical Judaism definitionally rejects Jesus Christ's sacrifice, and ask for proof. In fact, rabbinical Judaism teaches that it's a valid view that the Christ must suffer and that this suffering is somehow redemptive for his people; but they refuse to apply that the way Christianity does, and so they do not get the spiritual benefit of salvation from it.