[Satan’s Whisperings]

The answer—and Allah is the One who grants success and aid—is that the matter is as was said: Satan’s whisperings are not repelled by seeking refuge, as evidence for that is His, the Exalted, saying: "And We did not send before you any messenger or prophet except that when he recited, Satan cast into his recitation." [Al-Hajj:52] If whisperings were repelled by seeking refuge, the burden of duty would be lightened upon the believers.
What appears is that the benefit of seeking refuge is the drawing of additional divine gentlenesses, by which, when they occur, the effect of whisperings upon the believer diminishes. If these gentlenesses occur for the believer when he resorts to his Lord, they stand in the face of Satan’s whisperings, and the believer finds, because of them, strength to drive away Satan’s whisperings and to crush them. Indeed, no effect remains for them—even if they are present and occurring—yet they are subdued and overcome by the authority of the divine gentlenesses that the servant drew in when he resorted to his Lord and sought refuge with Him from their evil.

Source: Min Thimār al-ʿIlm wa al-Ḥikmah vol.3