Hadith 502870
Chapter 7: Tahajjud - كتاب صلاة الليل
وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ عَبْدِ الرَّحْمَنِ بْنِ الْقَاسِمِ، عَنِ الْقَاسِمِ بْنِ مُحَمَّدٍ، أَنَّهُ صَنَعَ مِثْلَ الَّذِي صَنَعَ ابْنُ عُمَرَ .
Yahya related to me from Malik from Abd ar-Rahman ibn al-Qasim that al-Qasim ibn Muhammad had done the same as Ibn Umar.
Reference Muwatta Malik 502870
USC-MSA web (English) reference : Book 7, Hadith 33