وَعَن مَالك بَلَغَهُ أَنَّ ابْنَ عَبَّاسٍ كَانَ يَقْصُرُ فِي الصَّلَاة فِي مثل مَا يكون بَين مَكَّة والطائف وَفِي مثل مَا يكون بَيْنَ مَكَّةَ وَعُسْفَانَ وَفَى مِثْلِ مَا بَيْنَ مَكَّةَ وَجُدَّةَ قَالَ مَالِكٌ: وَذَلِكَ أَرْبَعَةُ بُرُدٍ. رَوَاهُ فِي الْمُوَطَّأ
Malik said he heard that Ibn ‘Abbas used to shorten the prayer on a journey equivalent to that between Mecca and at-Ta'if, or between Mecca and ‘Usfan, or between Mecca and Judda. Malik said that that was four postal stages.
He and Ibn ‘Umar said that God’s Messenger established the practice of praying two rak'as when travelling, they constituting a complete observance and not an abbreviation; and the witr while travelling is a sunna.
Al-Bara’ said, "I accompanied God’s Messenger on eighteen journeys and I never saw him fail to pray two rak'as when the sun had passed the meridian before praying the noon prayer.”
Abu Dawud and Tirmidhi transmitted it, Tirmidhi saying that this is a gharib tradition.
Ibn ‘Abbas said, “God has prescribed the prayer by the tongue of your Prophet as four rak'as when resident, two when travelling, and one when danger is present.”