cellio | daf bit: Shevuot 2

(ShEvuot, as in "oaths", not ShAvuot, as in "weeks".)

The tractate opens with the mishna saying there are four types of oaths ("two, subdivided into four"), clarified by the g'mara: positive and negative, past and future: "I swear I shall", "I swear I shall not", "I swear I did", and "I swear I did not". It then talks about cases where information was known or unknown, and discusses the different ways that false oaths of different types are atoned for -- some by a sin offering he brings himself, some by the goat on Yom Kippur, some by the offerings brought on the new moon (Rosh Chodesh), and some by the offerings brought on festivals. Different rabbis assign them differently. In the g'mara, some rabbis say that there's no penalty for a future positive oath that turns out to be wrong ("I shall X" and you didn't X) because you didn't actually take an action. Others disagree. Given that we have positive commandments that you are liable for not doing, I'm not sure how that reasoning works (but I haven't read all the g'mara for this mishna yet).

The mishna talks mostly about oaths concerning actions taken while in a state of ritual impurity (tumah), distinguishing cases where you knew you were tamei but didn't know the action was prohibited, cases where you didn't know you were tamei but knew the action was prohibited to those in that state, cases where you knew but forgot, and more. The mishna occupies most of this daf (both sides), so I expect the g'mara to have more to say on all this.