Al-Kāfi - Volume 3 > Required Length of Distance of a Journey for Shortened Salah (Prayer)
Hadith #1

1ـ عَلِيُّ بْنُ إِبْرَاهِيمَ عَنْ أَبِيهِ عَنِ ابْنِ أَبِي عُمَيْرٍ عَنْ جَمِيلٍ عَنْ زُرَارَةَ عَنْ أَبِي جَعْفَرٍ (عَلَيْهِ الْسَّلام) قَالَ التَّقْصِيرُ فِي بَرِيدٍ وَالْبَرِيدُ أَرْبَعَةُ فَرَاسِخَ.

1. Ali ibn Ibrahim has narrated from his father from ibn abu ‘Umayr from Jamil from Zurarah who has said the following: “Abu Ja’far, ‘Alayhi al-Salam, has said, ‘Salah (prayer) is reduced after traveling a distance of one barid and one barid is four farasikh (which is twelve miles).”’