What is the ruling on swearing falsely with the intention of covering up an old sin that has been repented from, and is expiation obligatory for that?

Lying is forbidden, and its prohibition is emphasized if a person swears an oath upon it. Repentance from it is obligatory. A Muslim must conceal himself if he commits what Allah has forbidden. If compelled to speak, he should use allusive and ambiguous language (ta'rid and tawriyah), as they provide a way out of lying. Swearing a false oath is a ghamees oath (a perjurious oath that plunges one into sin). The majority of scholars hold that no expiation is required for it, though Imam Al-Shafi'i deemed it obligatory. Paying expiation is more cautious.