And the 129th prohibition is that a person who is impure is forbidden from eating from the sacrifices.
The source of this commandment is G‑d's statement regarding a woman after childbirth, "She shall not touch anything holy."
The Sifra says, "The verse says, 'She shall not touch anything holy, nor may she enter the Temple.' Just as one who enters the Temple when impure is punished by kares, so too, one who eats from the sacrifices when impure is punished by kares."
The explanation — that the phrase, "She shall not touch," refers to one who eats — relies on the principle explained in tractate Makkos on G‑d's statement (exalted be He), "She shall not touch anything holy."
This is the passage from tractate Makkos: "For an impure person who eats sacrifices, the punishment is clearly written, 'An impure person who eats meat of a peace-sacrifice to G‑d will be cut off [from his people].' What is the source of the actual prohibition? From the verse, 'She shall not touch anything holy.' "
The Talmud continues, "The verse, 'She shall not touch anything holy,' prohibits one from eating. You say it prohibits eating? You could think it prohibits touching! The Torah therefore writes, 'She shall not touch anything holy and shall not enter the Sanctuary,' to compare sacrifices to the Temple: just as [entering] the Temple [when impure] is at the cost of one's life, so too [the prohibition regarding] the sacrifices is for something which costs one's life. And for touching, what loss of life is there! It must therefore refer to eating." And G‑d uses the word "touch," when it means, "eat," to teach that touching is [prohibited] like eating.
From these passages it is clear to you that an impure person who eats from the sacrifices intentionally is punished by kares. If he does so accidentally, he must bring an adjustable sacrifice (korban oleh v'yored), as explained in Positive Commandment 72.
The details of this mitzvah have been explained in the 13th chapter of tractate Zevachim.
