'A’isha (RAA) narrated that The Messenger of Allah (ﷺ) said:

"Whoever dies while he still has some fasts to make up (of the days of Ramadan), then his heir (any of them) should fast on his behalf.” Agreed upon.

وَعَنْ عَائِشَةَ رَضِيَ اَللَّهُ عَنْهَا; أَنَّ رَسُولَ اَللَّهِ ‏- صلى الله عليه وسلم ‏-قَالَ: { مَنْ مَاتَ وَعَلَيْهِ صِيَامٌ صَامَ عَنْهُ وَلِيُّهُ } مُتَّفَقٌ عَلَيْهِ [1]‏ .‏