Al-Kāfi

Hadith 424
fasting
6ـ أَحْمَدُ بْنُ مُحَمَّدٍ عَنْ عَلِيِّ بْنِ الْحُسَيْنِ عَنْ مُحَمَّدِ بْنِ الْحُسَيْنِ عَنْ أَبِيهِ قَالَ كَتَبْتُ إِلَى أَبِي الْحَسَنِ (عَلَيْهِ السَّلاَم) مَا تَقُولُ فِي التَّلَطُّفِ يَسْتَدْخِلُهُ الإِنْسَانُ وَهُوَ صَائِمٌ فَكَتَبَ لا بَأْسَ بِالْجَامِدِ.
6. Ahmad ibn Muhammad from has narrated from Ali ibn al-Husayn from Muhammad ibn al-Husayn from his father who has said the following: “I once wrote to abu al-Hassan and asked about one’s performing an enema when fasting. He (the Imam) wrote back, ‘It is not harmful with a solid substance (as opposed to liquid).”’
Source: Shaykh Muḥammad b. Yaʿqūb al-Kulaynī