Narrated by Abu Hurairah(Radhiallaho anho):

Allah’s Messenger (sallAllaahu `alaihi wasallam) said :

Whoever performs ablution, and performs his ablution perfectly, and then goes to the masjid and finds that the people had finished the prayer (in congregation), Allah will give him a reward like one who prayed in congregation and attended it; The reward of those who prayed in congregation will not be curtailed.

Sunan of Abu-Dawood 564