In transliterated Arabic: Ashadu la illaha il Allah, wa Muhammadur rasul Allah.
In translation to English: I believe that there is One God, and Muhammad is his messenger (prophet).
It is considered correct to refer to previous prophets, such as Jesus (in Arabic, Isa) as prophets (rasul), and some groups (notably certain Sufi mystics) will amend this declaration to mention prior prophets whose names are found in the Qur'an.