Al-Kāfi - Volume 4 > The Case of a Fasting Person’s Sniffling or Use of Eardrops or Enema
Hadith #6

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).”’