What is the punishment for one who does not fulfill a vow?

Allah praised the believers, stating that they fulfill their vows. The vow that must be fulfilled is the vow of obedience. If one is unable to fulfill it, then he must offer expiation for breaking an oath. And whoever is able to fulfill a vow of obedience but does not do so, commits a sin thereby and exposes himself to punishment, for failure to fulfill vows is a characteristic of hypocrites.