Al-Kāfi - Volume 4 > Rinsing One’s Mouth and Nostrils while Fasting
Hadith #1

1ـ عَلِيُّ بْنُ إِبْرَاهِيمَ عَنْ أَبِيهِ عَنِ ابْنِ أَبِي عُمَيْرٍ عَنْ حَمَّادٍ عَنْ أَبِي عَبْدِ الله (عَلَيْهِ السَّلاَم) فِي الصَّائِمِ يَتَوَضَّأُ لِلصَّلاةِ فَيَدْخُلُ الْمَاءُ حَلْقَهُ فَقَالَ إِنْ كَانَ وُضُوؤُهُ لِصَلاةِ فَرِيضَةٍ فَلَيْسَ عَلَيْهِ شَيْ‏ءٌ وَإِنْ كَانَ وُضُوؤُهُ لِصَلاةِ نَافِلَةٍ فَعَلَيْهِ الْقَضَاءُ.

1. Ali ibn Ibrahim has narrated from his father from ibn abu ‘Umayr from Hammad who has said the following: “I once asked abu ‘ Abd Allah, ‘Alayhi al-Salam, about a man who takes wudu’ (ablution) and water enters in his throat. 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).”’