Rambam - 1 Chapter a Day

When the court inadvertently errs and rules to eliminate one of the Torah's fundamental laws and the entire people acted according to their ruling, the court is exempt and each of the transgressors is obligated to bring a fixed sin-offering, as implied by Leviticus 4:13: "And a matter will lapse...," i.e., a matter, but not an entire fundamental law.

The court is never liable for a sacrifice unless they issue a ruling, nullifying a certain aspect of a prohibition, but maintaining others regarding matters that are not explicitly stated and elaborated upon in the Torah. Only in such a situation will the court be obligated to bring a sacrifice and those who follow their ruling exempt.

What is implied? They erred and ruled that it is permitted to bow down to a false deity, that it is permitted to transfer an article from one domain to another on the Sabbath, or that it is permitted to be intimate with a woman who is watching day to day because of zivah bleeding. This is considered as one who stated that there is no prohibition in the Torah against performing labor on the Sabbath, worshiping false deities, or being intimate with a niddah, eliminating the entire prohibition. This is not considered as an erroneous ruling, but rather as forgetting the matter. Therefore the court is exempt from bringing a sacrifice and anyone who acted upon their ruling is liable for a sin-offering individually.

If, however, they erred and issued a ruling, saying that one who transfers an article from one domain to another is liable, as implied by Exodus 16:29: "A man should not depart from his place," but it is permitted for one to throw or pass an article from one domain to another - alternatively, they eliminated one of the primary categories of forbidden labor, ruling that it is not considered as forbidden labor - they are liable.

Similarly, they are liable if they erred and issued a ruling, saying that someone who prostrates himself, spreading out his hands and feet is liable, as ibid. 34:14 states: "Do not prostrate yourself to a foreign god," but it is permitted for one to kneel on the ground without spreading out his hands and feet.

Similarly, they are liable if they erred and issued a ruling, saying that one who is intimate with a woman who is watching day to day because of zivah bleeding, as implied by Leviticus 15:26 "all the days of her flow," but if she discovered bleeding at night, it is permitted to be intimate with her - alternatively, they issued a ruling, saying that one whose wife began to experience menstrual bleeding in the midst of intimacy is permitted to withdraw from her while erect.

Similarly, they are liable if they erred and stated that one is liable for partaking of blood which emerges from an animal at the time of ritual slaughter, but one who partakes of blood that collects in the heart is not liable. Similar laws apply with regard to all analogous errors. If they issued such rulings and the majority of the congregation acted because of their ruling, the people are exempt and the court must bring a sacrifice because of their error.

If the court ruled that the Sabbath ended because the sun became covered with clouds and it appeared to have set, and then it shined forth again, this is not considered as a mistaken ruling, but as an error. Any individual who performed a forbidden labor as a result is obligated to bring a sin-offering, but the court is exempt.

Similarly, if the court granted a married woman license to remarry, because testimony was delivered in their presence that her husband had died and then her husband appeared this is not considered as a mistaken ruling, but as an error. The woman and her second husband are obligated to bring a sin-offering for their inadvertent transgression. Similar laws apply in all analogous situations.

When a court delivers an erroneous ruling and then forgot the nature of the prohibition concerning which they ruled, they are exempt and those who transgressed as a result of their ruling are liable. This applies even if they have definite knowledge that they erroneously caused the violation of a prohibition and even when the people inform them about their ruling, telling them: "You ruled concerning this-and-this." This is derived from Leviticus 4:14: "And the transgression which they caused to be violated became known to them," i.e., they became aware of it on their own, rather than being informed about it by the transgressors.

What is implied? The court erred and ruled that the fat on the stomach was permitted and the majority of the people partook of it. Afterwards, they became aware that they issued an erroneous ruling and permitted an entity for which one would be liable for karet had one partaken of it willfully or a fixed sin-offering if one partook of it inadvertently. They were in doubt, however, if they ruled that some forbidden fat was permitted or that some forbidden blood was permitted. In such a situation, the court is exempt and all those who partook of the forbidden fat must bring a fixed sin-offering.

The following rules apply when the court ruled erroneously and then became aware of their error. Whether they already brought a sacrifice as atonement or did not yet bring one, whenever one transgresses because of their erroneous ruling that was disseminated throughout the Jewish people after they became aware of their error, the transgressor must bring a provisional guilt-offering. The rationale is that since he should have continually inquired about the new developments in the court, but failed to do so, he is considered like one who is in doubt whether he transgressed or not.

To whom does the above apply? To one who is in the same region as the court. If, however, one saw the initial, erroneous ruling and then journeyed to another region, he is exempt even if he transgressed after the court became aware of their error, because he relied upon them and cannot inquire about their rulings in his present place. Moreover, even if a person who is hurrying to depart, but has not yet set out on his journey, acts on their ruling after they became aware of their error, he is also exempt from bringing a provisional guilt-offering.