Is it permissible to retract a vow after fulfilling part of it, or must it be completed?

Whoever vows obedience to Allah Almighty is obligated to fulfill it, and it is not permissible to change it, due to Allah’s saying: {And let them fulfill their vows} [Al-Hajj: 29], and due to the Prophet’s (peace and blessings be upon him) saying: "Whoever vows to obey Allah, let him obey Him." If he is temporarily unable to fulfill it, he should wait until he is able to fulfill it, even though making vows is disliked.