كتاب صلاة المسافرين وقصرها
6  
The Book of Prayer - Travellers
(1)
Chapter: The travelers’ prayer and shortening it
(1)
باب صَلاَةِ الْمُسَافِرِينَ وَقَصْرِهَا ‏‏
Sahih Muslim 686 b

Ya'la b. Umayya reported:

I said to 'Umar b. al-Khattab, and the rest of the hadlth is the same.
Reference : Sahih Muslim 686b
In-book reference : Book 6, Hadith 5
USC-MSA web (English) reference : Book 4, Hadith 1462
  (deprecated numbering scheme)