Is expiation obligatory for one who swore by God that he did not cross a forbidden road, while he is unsure whether he had crossed it previously or not, even though he is certain that he has not crossed it for two years or more?

There is no expiation for swearing an oath concerning a past event, according to the majority of scholars, whether it is a laghw (vain) oath or a ghamus (perjurious) oath.

If the swearer believes what he is swearing about to be true, then there is no sin or expiation upon him.

However, if he deliberately lied about a past event (ghamūs oath), there is no expiation for it; rather, repentance is obligatory, because it is too grave to be expiated.

As for an oath concerning a past event with doubt about it, the Malikis consider it a ghamūs oath that necessitates sin and repentance, but not expiation.