Al-Kāfi - The Book of Fasting

Chapter: Rinsing One’s Mouth and Nostrils while Fasting 1ـ عَلِيُّ بْنُ إِبْرَاهِي٠َ عَنْ أَبِيهِ عَنِ ابْنِ أَبِي عُ٠َّادٍ عَنْ أَبِي عَبْدِ الله (عَلَيْهِ السَّلاَ٠ِ يَتَوَضَّأُ لِلصَّلاةِ فَيَدْخُلُ الْ٠َاءُ حَلْقَهُ فَقَالَ إِنْ كَانَ وُضُوؤُهُ لِصَلاةِ فَرِيضَةٍ فَلَيْسَ عَلَيْهِ شَيْ‏ءٌ وَإِنْ كَانَ وُضُوؤُهُ لِصَلاةِ نَافِلَةٍ فَعَلَيْهِ الْقَضَاءُ.

He (the Imam) said, ‘If his wudu’ (ablution) is for an obligatory Salat (prayer) there is not anything on him, but if it is for an optional Salat (prayer); he is required to make its Qada’ (compensatory fast).”’ حسن - Allamah Baqir al-Majlisi (Mirʾāt al-ʿUqūl fī Sharḥ Akhbār Āl al-Rasūl (16/283))