الكافي- ط الاسلامية, volume 4, page 130

1. A number of our people have narrated from Sahl ibn Ziyad from Mansur ibn al-‘Abbas from Muhammad ibn ‘Abd Allah ibn Wash from ‘Isma‘il ibn Sahl from a man who has said the following: “Once abu ‘Abd Allah (a.s.), commenced a journey just a few days before the end of the month of al-Sha‘ban and he (the Imam) was fasting. The month of Ramadan then started while he (the Imam) was still on his journey but he stopped fasting. He (the Imam) was asked, ‘How is it that you have been fasting in the month of al-Sha‘ban and stopped fasting in the month of Ramadan?’ He (the Imam) said, ‘In the case of the month of al-Sha‘ban it is up to me to fast or not to fast: however, in the case of the month of Ramadan it is the commandment of Allah, most Majestic, most Glorious, to stop fasting (on a journey).’”

Translation: Muhammad Sarwar·Thaqalayn link·The Arabic above is the original.

2. Muhammad ibn Yahya has narrated from Ahmad ibn Muhammad from Ahmad ibn Hilal from ‘Amr ibn ‘Uthman from ‘Adhafir who has said the following: “I once said to abu ‘Abd Allah (a.s.), that I fast these three days of the month but perhaps I travel or become ill, am I required to complete its Qada’ (compensatory fast)? He (the Imam) said, ‘Qada’ (compensatory fast) is obligatory for obligatory fast which is missed. In the case of optional fast it is up to you.’ I then asked, ‘Is it up to one’s choice even when on a journey and in illness?’ He (the Imam) said, ‘In the case of illness Allah, most Majestic, most Glorious, has exempted you, but in the case of journey you can complete its Qada’ (compensatory fast) and if you did not do so it is not harmful.’”

Translation: Muhammad Sarwar·Thaqalayn link·The Arabic above is the original.

3. A number of our people have narrated from Ahmad ibn Muhammad from Muhammad ibn Khalid from Sa‘d ibn Sa‘d al-Ash’ariy who has said the following: “I once asked al-Rida’ (a.s.), about the case of the three days’ fasting every month, if Qada’ (compensatory fast) is required from a traveler. He (the Imam) said, ‘No, he is not required to fast.’”

Translation: Muhammad Sarwar·Thaqalayn link·The Arabic above is the original.

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).”’

Translation: Muhammad Sarwar·Thaqalayn link·The Arabic above is the original.