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).'" (RU)
English reference (RU): Vol. 1, Book 1, Hadith 301 (RU)
Arabic reference (RU): Book 1, Hadith 320 (RU)