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.
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.”
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.
‘A’isha said that the prayer was prescribed as consisting of two rak'as, and after God's Messenger emigrated it was prescribed as four, but prayer while travelling was left according to the original prescription. Zuhri said he asked ‘Urwa why ‘A’isha said prayers in the complete form and he replied that she interpreted the matter herself as ‘Uthman did.