[If] someone is going to slaughter his pesach-offering, to circumcise his son, or to dine at a betrothal feast at the house of his father-in-law, and he remembers that he has chametz at home —- if he is able to return, remove [it], and [then] return to his mitzvah, he must go back and remove [it]; but if not, he nullifies it in his heart.  [If he is on his way] to save [people] from a [marauding] troop, from a river, from bandits, from a fire, or from a collapsed building, he nullifies it in his heart. [If] it was but to establish a voluntary resting place, he must return at once.

Similarly, [if] someone left Jerusalem and remembered that he had sacrificial meat in his hand —- if he has passed Tzofim, he burns it where he is; but if not, he [must] return and burn it before the Temple with the wood of the [altar] pyre.  And for how much [chametz or meat] must they return? — R' Meir says: In either case, [when there is] as much as an egg; R' Yehudah says: In either case, [when there is] as much as an olive. but the Sages say: [For] sacrificial meat, as much as an olive, but [for] chametz, as much as an egg.

Where it is customary to do work on the eve of Pesach until midday, we may do [work], [but] where it is customary not to do [work], we may not do [work].  [If] one goes from where they do [work] to where they do not, or from where they do not to where they do, we lay upon him the stringencies of the place which he has left and the stringencies of the place to which he has gone. But let no man deviate [from local custom], to avoid conflict.

Similarly, one who transports crops of the Sabbatical year from a place where they have been exhausted to a place where they have not been exhausted, or from a place where they have not been exhausted to a place where they have been exhausted, is required to remove [them].  R' Yehudah says: We say to him, “Go out and bring for yourself.”