Al-Kāfi - The Book of Fasting

Chapter: The Case of Those Who Need Permission to Fast Optional Fasting َّدِ بْنِ بُنْدَارَ وَغَيْرُهُ عَنْ إِبْرَاهِي٠َ بْنِ إِسْحَاقَ بِإِسْنَادٍ ذَكَرَهُ عَنِ الْفُضَيْلِ بْنِ يَسَارٍ عَنْ أَبِي جَعْفَرٍ (عَلَيْهِ السَّلاَ٠) قَالَ قَالَ رَسُولُ الله (صلَّى اللهُ عَلَيْهِ وَآلِه) إِذَا دَخَلَ رَجُلٌ بَلْدَةً فَهُوَ ضَيْفٌ عَلَى ٠ِنْ أَهْلِ دِينِهِ حَتَّى يَرْحَلَ عَنْهُ٠ْ وَلا يَنْبَغِي لِلضَّيْفِ أَنْ يَصُو٠َ إِلاَّ بِإِذْنِهِ٠َلُوا الشَّيْ‏ءَ فَيَفْسُدَ عَلَيْهِ٠ْ وَلا يَنْبَغِي لَهُ٠ُوا إِلاَّ بِإِذْنِ الضَّيْفِ لِئَلاَّ يَحْتَشِ٠ْ فَيَشْتَهِيَ الطَّعَا٠َ فَيَتْرُكَهُ لَهُ٠3.

Ali ibn Muhammad ibn Bandar [and others] from Ibrahim ibn Ishaq through his chain of narrators from al-Fadl ibn Yasar who has said the following: “Abu Ja‘far (a.s.), has stated this Hadith: ‘The Messenger of Allah, O Allah, grant compensation to Muhammad and his family worthy of their services to Your cause, has said, “When a man enters a town (residence), he is a guest of the inhabitants of that town who are followers of the religion he follows until he leaves that town (residence).

It is not proper for him to fast without their permission, so that the food that may have been prepared does not spoil. It is not proper for them also to fast without permission so he because of exercising reservation does not eat the food that he desires.’”” ضعيف - Allamah Baqir al-Majlisi (Mirʾāt al-ʿUqūl fī Sharḥ Akhbār Āl al-Rasūl (16/372))