Musannaf Ibn Abi Shaybah

Hazrat Ata narrates that a man performed the morning prayer with the Prophet Muhammad (peace and blessings be upon him). When the Prophet (peace and blessings be upon him) finished the prayer, that man stood up and performed two rak‘ahs. The Prophet (peace and blessings be upon him) asked him: "What are these two rak‘ahs?" He replied: "O Messenger of Allah (peace and blessings be upon him)! I came (to the mosque) when you were already in prayer, and I had not yet performed the two rak‘ahs before Fajr. I disliked that you were leading the prayer and I should perform those two rak‘ahs. So when you completed the prayer, I performed those two rak‘ahs." The narrator says: The Prophet (peace and blessings be upon him) neither ordered him nor forbade him (from this).