The 146th mitzvah is that we are commanded to slaughter an animal [we wish to eat] and only after that to eat it; and the only acceptable preparation is through shechitah.
The source of this commandment is G‑d's statement1 (exalted be He), "And you shall slaughter your cattle and sheep ... as I have commanded you."
In the words of the Sifri, "'And you shall slaughter' teaches that just as sacrifices need shechitah, so too non-sanctified animals need shechitah. 'As I have commanded you' teaches that Moshe was commanded regarding the trachea, and the esophagus, and cutting the majority of one for a bird, and cutting the majority of both for an animal."
The details of this mitzvah and all its laws are explained in the tractate devoted to this subject, i.e. tractate Chullin.
