´It was narrated from Ibn 'Abbas' that :` Sa'd bin 'Ubadah asked the Messenger of Allah (ﷺ) about a vow which his mother had made, but she had died without fulfilling it. The Messenger of Allah (ﷺ) said: "Fulfill it on her behalf ."
Hadith ReferenceSunan Ibn Majah / The Chapters on Expiation / Hadith: 2132
Hadith Gradingالألبانی:صحيح | زبیر علی زئی:متفق عليه