What is the number of expiations (kaffarat) required for a person who swore to fast three days then broke the oath, then swore to fast ten days then broke the oath, and does the ruling differ if he swore not to pray Dhuhr in congregation then broke the oath, then swore not to pray Asr in congregation then broke the oath?

If a person breaks multiple oaths whose cause is one before expiating them, then only one expiation is required of him. As for an oath to fast for an unspecified number of days, it can be fulfilled at any time, and the one who swore the oath has the choice between fulfilling it or offering expiation, and a single expiation suffices him. An oath to abandon congregational prayer – which is obligatory – is an oath to abandon a duty, so breaking it is obligatory and fulfilling it is forbidden.

As for one who swore an oath to commit a forbidden act or abandon an obligation, breaking the oath is obligatory for him, and fulfilling it is forbidden.