293. Eight Days a Week: The obligation to offer only animals that are at least eight days old

Any animal offered as a sacrifice must be at least eight days old. Our verse specifies that it must spend the first week of its life with its mother before it would be considered fit for use as an offering. An animal before this time is called a “mechusar z’man” – one “lacking time.”

The implication of this verse is “do not offer animals under eight days old” but a “lav haba m’klal asei” (negative inferred from a positive) is still counted as a positive mitzvah. (A practical difference would be that the courts did not impose punishment for violating a positive command – see Talmud Chulin 81a.)

The Sefer HaChinuch attributes this mitzvah to offering only the best animals as sacrifices and that, prior to eight days old, a newborn animal is not fit to be offered. The Chizkuni on this verse suggests that before eight days, an animal simply might not prove viable. Another reason might be as a kindness to the mother animal; after enduring pregnancy, it would be cruel of us not to permit her to indulge the instinct to nurse her calf.

This mitzvah applied in Temple times, to kohanim, who offered the sacrifices. (No person was permitted to consecrate a mechusar z’man for use as a sacrifice but if one did, it would not be considered a punishable offense.) It is discussed in the Talmud in tractate Zevachim on pages 112b and 114a-115a, and in Chulin on pages 22a-b (regarding birds) and 80b-81a. This prohibition is codified in the Mishneh Torah in the third chapter of Hilchos Issurei Mizbe’ach and is #60 of the 248 positive mitzvos in the Rambam’s Sefer HaMitzvos.