Shevuot 27: An Uttered Oath or an Oath in Vain
A new Mishnah! With exceptions to the basic laws of oaths - for example, if one swears not to fulfill a mitzvah. Rabbi Yehudah ben Beterah says that one who makes an oath that you're not allowed to make would still entail a violation, but the Tanna Kama seems to think that it wouldn't count as violating. Likewise, an issue to swear on a mitzvah to keep it. Plus, another new mishnah! Different wordings of swearing off something, though in the end, he would only be held accountable or on punishment. This "shevuot bitui" - risks the false oath in the intentional breaking of the oath - and needing lashes.. And an oath in vain?