Is one expiation of an oath obligatory, or two, for one who breaks a vow and a pledge to commit a sin?

A covenant with God is considered an oath. A vow to commit a sin is impermissible to undertake or to fulfill. What is obligatory in such a case is repentance and seeking forgiveness. Some scholars have held that an expiation for an oath (kaffarat yamin) is obligatory in this regard, and this is the more cautious opinion, based on the hadith: "There is no vow in disobedience, and its expiation is the expiation of an oath." If a vow and a covenant pertain to the same matter, then only one expiation is required.