For one afflicted with doubt in his faith

A`ūdhu billāh (Say:) I seek refuge in Allah. (Then you should desist from doing what you are in doubt about.) Reference: Al-Bukhari, cf. Al-Asqalani, Fathul-Bari 6/336, Muslim 1/120.
Āmantu billāhi wa Rusulih. (Say:) I believe in Allah and His Messengers. Reference: Muslim, 1/119-20.
Huwa ‘l-Awwalu wa ‘l-Ākhir, waẓ-Ẓāhiru wal-Bāṭin, wa huwa bikulli shay'in `Alīm. (Recite the Ayat) He is the First and the Last, the Most High and the Most Near. And He is the Knower of all things (in Arabic). Reference: Al-Hadid 57:3, Abu Dawud 4/329. Al-Albani graded it good in SahihAbu Dawud, 3/962.