بُلُوغُ الْمَرَامِ
Bulugh al-Maram 440
The Book of Prayer
وَعَنْ اِبْنِ عَبَّاسٍ رَضِيَ اَللَّهُ عَنْهُمَا قَالَ: قَالَ رَسُولُ اَللَّهِ - صلى الله عليه وسلم -: { لَا تَقْصُرُوا اَلصَّلَاةَ فِي أَقَلَّ مِنْ أَرْبَعَةِ بُرُدٍ; مِنْ مَكَّةَ إِلَى عُسْفَانَ } رَوَاهُ اَلدَّارَقُطْنِيُّ بِإِسْنَادٍ ضَعِيف ٍ [1] وَالصَّحِيحُ أَنَّهُ مَوْقُوفٌ، كَذَا أَخْرَجَهُ اِبْنُ خُزَيْمَةَ.
Narrated Ibn 'Abbas (RA): Allah's Messenger (ﷺ) said: "Do not shorten the prayer (while travelling) for a distance of less than four Burud; from Makkah to 'Usfan." [ad-Daraqutni reported it through a weak chain of narrators, and the right opinion is that it is Mawquf (saying of a companion, i.e. Ibn 'Abbas). Ibn Khuzaima reported it as such]. Burud: Plural of Barid, which means three Farsakh, and one Farsakh is equal to three miles.
Sunnah.com reference: Book 2, Hadith 354