´It was narrated from Sa'd bin 'Ubadah that he consulted the Prophet about a vow which his mother had to fulfill, but she died before doing so. The Messenger of Allah said:` "Fulfill it on her behalf."
Hadith ReferenceSunan an-Nasa'i / The Book of Wills / Hadith: 3687
Hadith Gradingالألبانی:صحيح الإسناد | زبیر علی زئی:حسن