It is narrated from Wabisah bin Ma'bad (may Allah be pleased with him) that he (peace and blessings be upon him) saw a man who was praying alone behind the row. He (peace and blessings be upon him) ordered him "to pray again."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 5208