Vowing to slaughter an animal every year if her son lives

Q: Every baby boy I gave birth to died. When I gave birth to my last baby boy, I vowed that if he lived, I would offer a yearly sacrifice on the 27th of Rajab, which is what people call "Rajabiyah." I fulfilled my vow for years until I learned that such a sacrifice is a Bid‘ah (innovation in religion). Now, I fear that my choice of this day may be sinful. Is it permissible for me to fulfill my vow on this day specifically, or should I change it, or there is nothing wrong with this? Please advise. May Allah reward you.

A: You must slaughter the sacrificial animal and offer its meat to the poor and the needy each year as you vowed, out of gratitude to Allah (Exalted be He), but on any day other than the one you specified, i.e. The twenty-seventh of Rajab.May Allah grant us success. May peace and blessings of Allah be upon our Prophet Muhammad, his family, and Companions.