It is narrated from Sayyiduna Ali (may Allah be pleased with him) that he led the people in prayer while in a state of major ritual impurity (janabah); he repeated the prayer himself, then he ordered them and they also repeated it.
Only Amr bin Khalid Abu Makhlad al-Wasiti narrates this, and he is matruk (abandoned); the hadith masters accused him of lying.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4078