Al-Kāfi - Volume 3 > Where to Apply Rules about Salah (Prayer) on a Journey
Hadith #6

6ـ مُحَمَّدُ بْنُ يَحْيَى عَنْ مُحَمَّدِ بْنِ الْحُسَيْنِ عَنْ صَفْوَانَ عَنِ الْعِيصِ بْنِ الْقَاسِمِ قَالَ سَأَلْتُ أَبَا عَبْدِ الله (عَلَيْهِ الْسَّلام) عَنْ رَجُلٍ صَلَّى وَهُوَ مُسَافِرٌ فَأَتَمَّ الصَّلاَةَ قَالَ إِنْ كَانَ فِي وَقْتٍ فَلْيُعِدْ وَإِنْ كَانَ الْوَقْتُ قَدْ مَضَى فَلاَ.

6. Muhammad ibn Yahya has narrated from Muhammad ibn al-Husayn from Safwan from ‘Is ibn al-Qasim who has said the following: “I once asked abu ‘Abd Allah, ‘Alayhi al-Salam, about a man who on a journey performs Salah (prayer) in complete form. He (the Imam) said, ‘If there is time for it he is required to perform his Salah (prayer) again, otherwise, it is passed.’”