Hadith 3
Chapter 11: The Fear Prayer - كتاب صلاة الخوف
Malik said that Nafi said, "I do not believe that Abdullah ibn Umar related it from anyone other than the Messenger of Allah, may Allah bless him and grant him peace."
Reference Muwatta Malik 3
USC-MSA web (English) reference : Book 11, Hadith 3