It is narrated from Muhammad bin Amr that Sayyiduna Uthman bin Affan (may Allah be pleased with him) led the people in prayer while in a state of major ritual impurity (janabah). In the morning he saw traces of janabah on his clothes and began saying: I have grown old; by Allah! I find myself in a state of janabah and yet I do not know it. Then he (may Allah be pleased with him) repeated the prayer, and he did not order the others to repeat the prayer.
Abd al-Rahman (may Allah have mercy on him) said: There is agreement on this issue that the one in a state of janabah repeats his prayer, but the others do not repeat it. I do not know of any disagreement about it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4074