“Name... Harry Potter. Crime...”
“It was only a bit of mud!” said Harry. “It’s only a bit of mud to you, boy, but to me it’s an extra hour scrubbing!” shouted Filch, a drip shivering unpleasantly at the end of his bulbous nose. “Crime... befouling the castle... suggested sentence...”

Harry Potter and the Chamber of Secrets - Chapter 8 : The Deathday Party
See this quote in the Pensive -