Vowing to slaughter an animal every year if her son lives

Q: A mother vowed to slaughter an animal every year if her son lived until he would be able to serve her. He has already attained maturity and has begun helping her. She fulfilled the vow for some years until two years ago when someone told her that she was not obligated to slaughter an animal every year. She asks for your Fatwa concerning this.

A: What the woman did by fulfilling her vow and slaughtering an animal every year, after her son began serving her, is required from her. She will be rewarded for this In sha’a-Allah (if Allah wills). She must continue doing so, as long as she has the means to slaughter an animal every year. She must make up for the two sacrifices she missed over the past two years, in order for her vow to be complete. The Prophet (peace be upon him) said, Whoever vows to obey Allah should obey Him; and whoever vows to disobey Allah should not disobey Him. May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.