It was narrated that Qais bin 'Amr said: "The Prophet P.B.U.H saw a man praying two Rak'ah after the Subh prayer and said, 'Is the Subh prayer to be offered twice?' The man said to him: 'I did not pray the two Rak'ah before it, so I prayed them (now).' The Messenger of Allah P.B.U.H remained silent." (Sahih)