Sayyidah Aishah (may Allah be pleased with her) says that a man said to the Messenger of Allah (peace and blessings be upon him) (while I was listening): "I wake up in the morning in a state of janabah (major ritual impurity) and I intend to fast." He (peace and blessings be upon him) said: "I too wake up in the morning in a state of janabah and I intend to fast. I take a ritual bath (ghusl), then I fast that day." The man said: "You (peace and blessings be upon him) are not like us; your past sins have been forgiven, and the later ones too." The Messenger of Allah (peace and blessings be upon him) became angry and said: "By Allah, I hope that I am the most fearful of Allah among you, and the most knowledgeable of you about what taqwa (God-consciousness) is."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 7989