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-spreading.”
Allah the most Exalted also said:
“And whatever you spend for spending (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 (R.A.) that Allah’s Messenger (SAW) 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”. (Al-Bukhari)
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.