Sunan At-Tirmidhi

Qais narrated:""Allah's Messenger (S) went out and the Iqamah was called for the Salat so I prayed As-Subh with him. Then the Prophet (S) turned and found me performing Salat so he said: 'Easy O Qais! Are there two prayers together?' I said: 'O Messenger of Allah! I did not perform the two Rak'ah (before) Fajr.' He said: 'Then there is no harm