«إِنَّ بَدَنِي قَدِ اتَّسَخَ وَدَرَنِي قَدْ رَسَخَ»
My body has become dirty, and the grime upon me has settled deeply.
Abū Zayd frames a mundane problem in elegant parallel clauses. Ittasakha means to become dirty; rasakha to become firmly fixed; daran is dirt or grime.
The requested bath sounds reasonable. Yet this is a character already shown to use language persuasively. His artistry is not separate from the plot: it helps make the request convincing.