Sayyiduna Thabit bin Qays (may Allah be pleased with him) narrates: I came to the mosque while the Prophet (peace and blessings be upon him) was in prayer. When the Prophet (peace and blessings be upon him) concluded with the salam, he turned towards me while I was praying. The Prophet (peace and blessings be upon him) kept looking at me while I was praying. When I finished, he (peace and blessings be upon him) said: "Did you not pray with us?" I said: Yes indeed, O Messenger of Allah. He (peace and blessings be upon him) said: "Then what was this prayer?" I said: O Messenger of Allah, it was the two rak'ahs of Fajr; I left my house and had not prayed them. The narrator said: The Messenger of Allah (peace and blessings be upon him) did not find fault with me for that.
Hadith Referenceالمعجم الكبير للطبراني / باب الثاء / 1306