Dawud bin Abi Hind said: I asked Sa'id bin al-Musayyib, may Allah have mercy on him, that if a man has already performed prayer in his house, then finds the Imam leading prayer, should he pray with that Imam? Sa'id bin al-Musayyib, may Allah have mercy on him, said: Yes, he should pray. I asked: Then which of the two prayers will be counted as obligatory? Ibn al-Musayyib, may Allah have mercy on him, said: The one performed with the Imam. Our master Abu Hurairah, may Allah be pleased with him, narrated to us that the Messenger of Allah, peace and blessings be upon him, said: "A man's prayer with the congregation is better than his prayer alone by more than twenty times."