Sunan Abi Dawud Book 2, Hadith 188
if one of us prays in his house, then comes to the mosque and finds that the iqamah is being called, and if I pray along with them ( in congregation), I feel something inside about it. Abu Ayyub replied: We asked the Prophet (ﷺ) about it. He said: That is a share from the spoils received by the warriors (i.e. he will receive double the reward of the prayer).
I came while the Prophet (ﷺ) was saying the prayer. I sat down and did not pray along with them. The Messenger of Allah (ﷺ) turned towards us and saw that Yazid was sitting there. He said: Did you not embrace Islam, Yazid? He replied: Why not, Messenger of Allah; I have embraced Islam. He said: What prevented you from saying prayer along with the people? He replied: I have already prayed in my house, and I thought that you had prayed (in congregation). He said: When you come to pray (in the mosque) and find the people praying, then you should pray along with them, though you have already prayed. This will be a supererogatory prayer for you and that will be counted as obligatory.
Sulayman, the freed slave of Maymunah, said: I came to Ibn Umar at Bilat (a place in Medina) while the people were praying. I said: Do you not pray along with them? He said: I heard the Messenger of Allah (ﷺ) say: Do not say a prayer twice in a day.