To vow to other than Allah is an act of Shirk
Allah the Most Exalted said: “They (are those who) fulfill (their) vows, and they fear a Day whose evil will be wide-
Allah the Most Exalted also said: “And whatever you spend for spendings (e.g. in Sadaqah charity etc. for Allah’s cause) or
whatever vow you make, be sure Allah knows it all.” (2:270)
Narrated ‘Aishah (May Allah be pleased with him) that Allah’s Messenger (May the peace and blessing of Allah be upon him) said: “Whoever vows that he will be obedient to Allah, he should be obedient to Him; and whoever made a vow that he will disobey Allah, he should not disobey Him”.
Important issues of the Chapter
1) Fulfillment of the vow is obligatory.
2) Since it is approved that making a vow is an act of worship to Allah, then directing a vow to other than Allah is committing Shirk.
3) Any vow based on disobedience (to Allah the Almighty) is impermissible to be carried out.