Ibn 'Umar Radiyallahu 'Anhu says:
"I memorised from Rasulullah Sallallahu 'Alayhi Wasallam eight raka-aat; two before zuhr and two after zuhr; two rak'ahs after maghrib and two after 'eshaa". Ibn 'Urnar Radiyallahu'Anhu said.. "Hafsah related to me about the two rak'ahs of the morning, which I did not observe from Rasulullah Sallallahu'Alayhi Wasallam". (DE)
English reference (DE): Book 39, Hadith 269 (DE)
Arabic reference (DE): Book 40, Hadith 285 (DE)