'Aishah (May Allah be pleased with her) said:
The Prophet ﷺ said, "If a person dies without observing Saum (fasts), his Wali should make it up on his behalf."

[Al-Bukhari and Muslim].

وعنها رضي الله عنها عن النبي ﷺ قال: "من مات وعليه صوم، صام عنه وليه" ((متفق عليه)).