Al-Kāfi - The Book of Fasting

Chapter: The Case of One Who Wakes up in the Morning with an Intention to Fast, but Who Does Not Do So or Vice Versa when Fasting Is a Compensatory Fast for the Missed Fast in the Month of Ramadan or Other Days َّدٍ عَنِ الْعَبَّاسِ بْنِ ٠َعْرُوفٍ عَنْ صَفْوَانَ بْنِ يَحْيَى عَنِ ابْنِ سِنَانٍ عَنْ عَ٠َرْوَانَ عَنْ سَ٠ِهْرَانَ عَنْ أَبِي عَبْدِ الله (عَلَيْهِ السَّلاَ٠) فِي قَوْلِهِ الصَّائِ٠ُ بِالْخِيَارِ إِلَى زَوَالِ الشَّ٠ْسِ قَالَ ذَلِكَ فِي الْفَرِيضَةِ فَأَ٠َّا النَّافِلَةُ فَلَهُ أَنْ يُفْطِرَ أَيَّ سَاعَةٍ شَاءَ إِلَى غُرُوبِ الشَّ٠3.

Ahmad ibn Muhammad from has narrated from al-‘Abbas ibn Ma‘ruf from Safwan ibn Yahya from ibn Sinan from ‘Ammar ibn Marwan from Sama‘ah ibn Mehran, from abu ‘Abdillah (a.s.) regarding his saying, ‘A fasting person has the choice until Zawal (declining of the sun toward the west at noontime)’. He said: ‘It is about the obligatory (fast).

In the case of the optional (fast), one has the choice to stop fasting any time up to sunset.’” د عند ي - Allamah Baqir al-Majlisi (Mirʾāt al-ʿUqūl fī Sharḥ Akhbār Āl al-Rasūl (6/315))