CHAPTER: When Should The Traveler Shorten The Prayer?
Narrated Yahya bin Yazid al-Hannani: I asked Anas bin Malik about the shortening of the prayer (while travelling). He said: When the Messenger of Allah صلی اللہ علیہ وسلم went out on a journey of three miles or three farsakh (the narrator Shubah doubted), he used to pray two rak'ahs.
Narrated Anas bin Malik: I prayed along with the Messenger of Allah صلی اللہ علیہ وسلم four rak'ahs at the noon prayer at Madina and two rak'ahs at the afternoon prayer in Dhu al-Hulaifah.