Dua for doubt in faith
Dua 1:
هُوَ الْأَوَّلُ وَالْآخِرُ وَالظَّاهِرُ وَالْبَاطِنُ ، وَهُوَ بِكُلِّ شَيْءٍ عَلِيْمٌ
Translation :
He is the First and the Last, the Most High and the Most Near. And He is All-Knowing about everything.
Transliteration :
Huwa-l-Awwalu wa-l-Ākhiru wa-ẓ-Ẓāhiru wa-l-bāṭin, wa Huwa bi-kulli shay’in ‘Alīm.
Hadith:
Abu Zumayy reported: “I asked Ibn Abbas (radiy Allāhū ‘anhumā): ‘What is this that I am experiencing?’ He answered: ‘What is it?’ I said: ‘By Allah, I cannot talk about it.’ He asked me: ‘Is it something to do with doubt?’ [When answered it was], he smiled and said: ‘No-one was safe from it until Allah revealed:
“If you are in doubt concerning what We revealed unto you [O Prophet], ask those who read the Scripture from before your time. The truth has indeed come to you from your Lord, so be not one of those in doubt.” (10:94)
Ibn Abbas (radiy Allāhū ‘anhumā) told me: ‘If you find any [doubt] within yourself, say: [the above].” (Abū Dāwūd 5110)
Dua 2:
آمَنْتُ بِاللهِ وَرُسُلِهِ
Translation :
I believe in Allah and His Messengers.
Transliteration :
Āmantu bi-llāhi wa rusulih.
Hadith:
The Messenger of Allah ﷺ said: “Shaytān comes to one of you and says: ‘Who created you?’ He replies: ‘Allah.’ Then Shaytān says: ‘Who created Allah?’ If that happens to any one of you, let him say [the above]. Indeed it will go away from him.” (Ahmad 25671)
The Messenger of Allah ﷺ said: “Whoever experiences any of these insinuations should say [the above] thrice, and it will leave him. (Ibn al-Sunnī 629)