Muwatta Malik #398
Shortening the Prayer
The Arabic includes the chain of narration (sanad) and the collector's commentary; the English translation shows the Prophet's words only.
وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ أَبِي جَعْفَرٍ الْقَارِئِ، أَنَّهُ قَالَ كُنْتُ أُصَلِّي وَعَبْدُ اللَّهِ بْنُ عُمَرَ وَرَائِي وَلاَ أَشْعُرُ فَالْتَفَتُّ فَغَمَزَنِي .
Yahya related to me from Malik that Abu Jafar al-Qari said, "I
was praying, and Abdullah ibn Umar was behind me and I was not aware
of it. Then I turned round and he prodded me (in disapproval)."
About Muwatta Malik
This hadith is #398 from Muwatta Malik, in the Book of Shortening the Prayer.