Prayer During Travel
Man Lā Yaḥḍuruh al-Faqīh|Volume 1|Book 1|Chapter 59
وَ أَمَّا خَبَرُ حَرِيزٍ عَنْ مُحَمَّدِ بْنِ مُسْلِمٍ عَنْ أَبِي عَبْدِ اَللَّهِ عَلَيْهِ اَلسَّلاَمُ قَالَ: سَأَلْتُهُ عَنْ رَجُلٍ يَدْخُلُ مِنْ سَفَرِهِ وَ قَدْ دَخَلَ وَقْتُ اَلصَّلاَةِ وَ هُوَ فِي اَلطَّرِيقِ قَالَ «يُصَلِّي رَكْعَتَيْنِ وَ إِنْ خَرَجَ إِلَى سَفَرِهِ وَ قَدْ دَخَلَ وَقْتُ اَلصَّلاَةِ فَلْيُصَلِّ أَرْبَعاً.
Regarding the report of Hariz from Muhammad ibn Muslim, from Imam Jafar ibn Muhammad Al-Sadiq عليه السلام, who said: "I asked him about a man who returns from his journey while the time for prayer has entered, and he is still on the road." Imam عليه السلام said: "He should pray two rak'ahs (units of prayer). If he sets out on a journey and the time for prayer has already entered, then he should pray four rak'ahs."
- Ṣaḥīḥ al-Faqīh, p. 64