Zevachim 8 - The Special Strictness of the Passover Offering
The Passover offering is more strict in that if one has the intention to bring it as a different sacrifice, it become completely invalid, the service stops, and the sacrifice is burnt together with other invalidated offerings.
From where do we know this fact? From the phrase "Watch the month of spring and make a Passover offering" we derive that all actions of the Passover sacrifice should be done in the name of that sacrifice, and not any other one.
However, from this we only know that the change of the designation ruins the sacrifice. How do we know that if the priest erroneously intends that the sacrifice should belong to someone other than its true owner, that this too makes it invalid? Because of the phrase, "Say, this is the Passover sacrifice". This phase is extra and not needed to teach the previous prohibition, so we apply it to the change in ownership.
However, so far we only know the requirement not to change the designation or the ownership of the sacrifice. How do we know that if we do change it, this makes the sacrifice completely invalid? From the phrase, "Slaughter the sacrifice for the Lord your God", meaning, every action should be done as commanded.
Art: Vincent Van Gogh - Fishing In Spring