Al-Kāfi - Volume 3 > Required Length of Distance of a Journey for Shortened Salah (Prayer)
Hadith #2

2ـ وَعَنْهُ عَنْ أَبِيهِ عَنِ ابْنِ أَبِي عُمَيْرٍ عَنْ أَبِي أَيُّوبَ قَالَ قُلْتُ لأَبِي عَبْدِ الله (عَلَيْهِ الْسَّلام) أَدْنَى مَا يَقْصُرُ فِيهِ الْمُسَافِرُ فَقَالَ بَرِيدٌ.

2. It is a narration from him (narrator of previous Hadith) by his father from ibn abu ‘Umayr from abu Ayyub who has said the following: “I once asked abu ‘Abd Allah, ‘Alayhi al-Salam, about the minimum distance after the traveling of which a traveler reduces his Salah (prayer). He (the Imam) said, ‘It is one barid.’”