It was narrated that Anas bin Malik said:
"Whenever the Prophet exited the toilet, he would say: 'Al-hamdu lillahilladhi adhhaba 'annial-adha wa 'afani (Praise is to Allah Who has relieved me of impurity and given me good health).'" (IT)
English reference (IT): Vol. 1, Book 1, Hadith 301 (IT)
Arabic reference (IT): Book 1, Hadith 320 (IT)