It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that he (peace and blessings be upon him) said: "Whoever performs ablution and does it well, then sets off and finds that the people have already prayed, Allah will give him a reward equal to that of those who prayed it and attended it, and nothing will be reduced from their reward."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 5010