Isma'il bin Zakaria bin Mrh إسماعيل بن زكريا بن مرة · The Chapters on Expiation

a woman came to the Messenger of Allah (ﷺ) and said: "My mother has died, and she had made a vow to fast, but she died before she could fulfill it. The Messenger of Allah (ﷺ) said: 'Let her guardian fast on her behalf ."