Abu Huraira reported God s Messenger as saying, “If anyone performs ablution, doing it well, then goes and finds that the people have finished the prayer, God will give him a reward equivalent to that of those who prayed and were present at it without that diminishing anything from their rewards.”
Anas reported God’s Messenger as saying, “If anyone prays to God for forty days in congregation being present in time for the first takbira, two immunities will be recorded for him, one from hell and one from hypocrisy,”
Abu Sa'id al-Khudri told how a man came when God’s Messenger had already prayed, and he said, “Will no one give alms* to this man and pray along with him?” Thereupon a man got up and prayed along with him.
* This is a literal translation. The idea is that by joining with him he increased the reward the man would receive for his prayer, as prayer in company has a much greater reward than prayer alone.
Abu Huraira reported God’s Messenger as saying, “When you come to the prayer and we are prostrating ourselves you must prostrate yourselves without reckoning it as part of your prayer; and if anyone is present at a rak'a he has been present at the prayer.”