Al-Kāfi - Volume 4 > Postponing the Three Days Fasting to Winter Months
Hadith #3

3ـ أَحْمَدُ بْنُ إِدْرِيسَ وَمُحَمَّدُ بْنُ يَحْيَى عَنْ مُحَمَّدِ بْنِ أَحْمَدَ عَنْ أَحْمَدَ بْنِ الْحَسَنِ عَنْ عَمْرِو بْنِ سَعِيدٍ عَنْ مُصَدِّقِ بْنِ صَدَقَةَ عَنْ عَمَّارِ بْنِ مُوسَى عَنْ أَبِي عَبْدِ الله (عَلَيْهِ السَّلاَم) قَالَ سَأَلْتُهُ عَنِ الرَّجُلِ يَكُونُ عَلَيْهِ مِنَ الثَّلاثَةِ أَيَّامِ الشَّهْرِ هَلْ يَصْلُحُ لَهُ أَنْ يُؤَخِّرَهَا أَوْ يَصُومُهَا فِي آخِرِ الشَّهْرِ قَالَ لا بَأْسَ قُلْتُ يَصُومُهَا مُتَوَالِيَةً أَوْ يُفَرِّقُ بَيْنَهَا قَالَ مَا أَحَبَّ إِنْ شَاءَ مُتَوَالِيَةً وَإِنْ شَاءَ فَرَّقَ بَيْنَهُمَا.

3. Ahmad ibn Idris and Muhammad ibn Yahya has narrated from Ahmad ibn Muhammad from Ahmad ibn al-Hassan from ‘Amr ibn Sa‘id from Musaddiq ibn Sadaqah from ‘Ammar ibn Musa who has said the following: “I once asked abu ‘Abd Allah, ‘Alayhi al-Salam, about a man who owes three days of fasting of every month if it is proper for him to delay and fast in the end of the month. He (the Imam) said, ‘It is not harmful.’ I then asked, ‘Should he fast with intervals in between or without it? He (the Imam) said, ‘Whichever way he likes, with or without interval as he chooses.’”