Parashas Vayikra · Aliyah 1 · Passuk 5
Chabad.org — English translation + Rashi
Torah Temima points to Chullin 13a (verified; unwitting slaughter of kodashim is invalid).
E-Daf.com — Tsurras Hadaf (size=3)
HebrewBooks / Shas PDF of the daf
English: “And he shall slaughter the young of the herd” — until the slaughter is for the sake of [this] young of the herd; from here: one who acts unwittingly with sacred animals — the act is invalid.
Custom (requirement of intention from the specified object) — the passuk names the animal so that the slaughter must be performed for its sake; absent that intention, kodashim shechita is invalid.
Unwitting slaughter of a sacrificial animal (e.g. playing with a knife that happens to cut the neck) is invalid. Ordinary chullin meat can be valid without that intention; kodashim require it.