Dont make vows, vows do not change destiny

 

Do not make vows , it does not change divine decree

But you should not make vows after that, because making vows is not appropriate. The Prophet (blessings and peace of Allah be upon him) said: “Do not make vows, for vows do not ward off anything of the divine decree; all they do is get something out of the miser.” 

So vows should not be made, by one who is sick or anyone else. But if a person does make a vow to do an act of obedience to Allah, such as prayer and fasting, then it becomes obligatory for him to fulfil it, because the Prophet (blessings and peace of Allah be upon him) said: “Whoever vows to obey Allah, let him do so, and whoever vows to disobey Allah, let him not do so.” Narrated by al-Bukhaari in as-Saheeh.

 

Complete Answer

https://islamqa.info/en/answers/130136/fasting-in-fulfilment-of-a-vow-nadhr-takes-precedence-over-fasting-six-days-of-shawwaal