Is persistent doubt concerning the existence of God, the Resurrection, and the Reckoning, coupled with outward devotion to God, considered disbelief and hypocrisy, and is there a remedy for such doubt?

Doubt about the existence of Allah and the Last Day is disbelief if it settles in the heart, unlike a fleeting thought that is repelled by seeking refuge [with Allah]. The whisperings with which Satan attacks without the servant's choice, and which the servant dislikes and repels, are a clear sign of faith, as opposed to doubt, which is a vacillation that shakes faith. Disliking the whisperings of disbelief and hypocrisy and the heart's fleeing from them is a clear sign of faith, and it is proof that Satan's cunning is limited to whisperings. Therefore, the believer must remain steadfast, patient, and adhere to remembrance [of Allah] and prayer to repel Satan's weak cunning.