Al-Kāfi

Hadith 516
fastingtravel-prayer
4ـ أَحْمَدُ بْنُ مُحَمَّدٍ عَنِ الْمَرْزُبَانِ بْنِ عِمْرَانَ قَالَ قُلْتُ لِلرِّضَا (عَلَيْهِ السَّلاَم) أُرِيدُ السَّفَرَ فَأَصُومُ لِشَهْرِيَ الَّذِي أُسَافِرُ فِيهِ قَالَ لا قُلْتُ فَإِذَا قَدِمْتُ أَقْضِيهِ قَالَ لا كَمَا لا تَصُومُ كَذَلِكَ لا تَقْضِي.
4. Ahmad ibn Muhammad has narrated from al-Marzuban ibn ‘Imran who has said the following: “I once asked al-Rida’ (a.s.), that I like to travel; can I fast in the month in which I am on a journey? He (the Imam) said, ‘No, you cannot do so.’ ‘Can I complete its Qada’ (compensatory fast) when I come home?’ I asked. He (the Imam) said, ‘No, just as you cannot fast in the same way you cannot carry out its Qada’ (compensatory fast).”’
Source: Shaykh Muḥammad b. Yaʿqūb al-Kulaynī