Sayyiduna Abu Bakrah (may Allah be pleased with him) says that the Messenger of Allah (peace and blessings be upon him) began the prayer, then signalled to them: "Stay in your places," and he (peace and blessings be upon him) went into his house. Then he came out with drops of water dripping from his (peace and blessings be upon him) head. The Prophet (peace and blessings be upon him) joined the prayer and led them in congregation. When he had completed the prayer, he said: "I too am only a human being; I was in a state of major impurity (janabah)."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 5150