Hadith
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
Sahih · Salim al-Hilali
Muwatta Malik 396 ·Book 9, Hadith 71·Also available on sunnah.com·