This sugya will deal with the halacha of "Oness B'Yom Acharon". If one pushed off fulfilling an obligation until the last minute, and then due to an oness (accident) he was unable to fulfill his obligation, does this constitute an exemption from his original obligation? This discussion obviously has many implications, such as if one postponed davening for later, etc.

One of the sources for this debate is found in Parshas Behar, where the Torah grants a 12-month buy-back option for a seller of a house under certain circumstances. What if he waited until the last minute, and was prevented from executing this option?