Al-Kāfi

Hadith 1698
travel-prayer
4ـ عَلِيُّ بْنُ إِبْرَاهِيمَ عَنْ أَبِيهِ عَنْ حَمَّادٍ عَنْ حَرِيزٍ عَنْ مُحَمَّدِ بْنِ مُسْلِمٍ قَالَ سَأَلْتُ أَبَا عَبْدِ الله (عَلَيْهِ الْسَّلام) عَنْ رَجُلٍ يَدْخُلُ مِنْ سَفَرِهِ وَقَدْ دَخَلَ وَقْتُ الصَّلاَةِ قَالَ يُصَلِّي رَكْعَتَيْنِ فَإِذَا خَرَجَ إِلَى سَفَرٍ وَقَدْ دَخَلَ وَقْتُ الصَّلاَةِ فَلْيُصَلِّ أَرْبَعاً.
4. Ali ibn Ibrahim has narrated from his father from Hammad, from Hariz from Muhammad ibn Muslim who has said the following: “I once asked abu ‘Abd Allah (a.s.), about a man who returns from his journey when it has become the time for a Salah (prayer). He (the Imam) said, ‘He is required to perform his Salah (prayer) as two Rak‘at and if he goes out on a journey when it has become the time for Salah (prayer) he is required to perform his Salah (prayer) as four Rak‘at.’”
Source: Shaykh Muḥammad b. Yaʿqūb al-Kulaynī