Vowing is an undesirable act for a Muslim, for it is authentically reported that the Prophet (peace be upon him) said:
A vow is not a means of bringing good but a means to extract good from the miserly people.
But in case that someone makes a vow to do some obedience to Allah, they should fulfill it, as the Prophet (peace be upon him) says:
Whoever vows that he will be obedient to Allah, should remain obedient to Him; and whoever makes a vow that he will disobey Allah, should not disobey Him.
Offering vows to anyone other than Allah is Shirk-Akbar (major form of associating others in worship with Allah), for it is an act of `Ibadah (worship) and offering `Ibadah to anyone other than Allah is Shirk (associating others with Allah in His Divinity or worship).May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.