وَ كَتَبَ مُحَمَّدُ بْنُ اَلْحَسَنِ اَلصَّفَّارُ رَضِيَ اَللَّهُ عَنْهُ إِلَى أَبِي مُحَمَّدٍ اَلْحَسَنِ بْنِ عَلِيٍّ عَلَيْهِ اَلسَّلاَمُ: فِي رَجُلٍ مَاتَ وَ عَلَيْهِ قَضَاءٌ مِنْ شَهْرِ رَمَضَانَ عَشَرَةُ أَيَّامٍ وَ لَهُ وَلِيَّانِ هَلْ يَجُوزُ لَهُمَا أَنْ يَقْضِيَا عَنْهُ جَمِيعاً خَمْسَةَ أَيَّامٍ أَحَدُ اَلْوَلِيَّيْنِ وَ خَمْسَةَ أَيَّامٍ اَلْآخَرُ فَوَقَّعَ عَلَيْهِ اَلسَّلاَمُ «يَقْضِي عَنْهُ أَكْبَرُ وَلِيَّيْهِ عَشَرَةَ أَيَّامٍ وِلاَءً إِنْ شَاءَ اَللَّهُ ».
Muhammad ibn al-Hasan al-Saffar, may Allah (swt) be pleased with him, wrote to Imam Abu Muhammad al-Hasan ibn Ali (a.s): Regarding a man who passed away and had ten days of fasting left from the Month of Ramadan, and he had two heirs. Is it permissible for both heirs to divide the days, with each fasting five days on his behalf? The Imam (a.s) replied in writing: "The eldest of the two heirs should fast all ten days consecutively, if Allah (swt) wills."