Hadith 503990
Chapter 9: Shortening the Prayer - كتاب قصر الصلاة فى السفر
وَحَدَّثَنِي عَنْ مَالِكٍ، أَنَّهُ بَلَغَهُ أَنَّ عَبْدَ اللَّهِ بْنَ مَسْعُودٍ، كَانَ يَدِبُّ رَاكِعًا .
Yahya related to me from Malik that he had heard that Abdullah ibn Masud used to move forward while in ruku.
Reference Muwatta Malik 503990
USC-MSA web (English) reference : Book 9, Hadith 68