Sunan Ibn Majah
301
Daif+2

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)

DaifAl-Albani
DaifMuhammad Fouad Abd al-Baqi