What is meant by "doubt" (al-ribah) in the noble verse: "The believers are only those who have believed in Allah and His Messenger and thereafter have not doubted" (Quran 49:15)? What are its manifestations and forms, and does this include what is beyond human control?

Those who have no doubt are those who have affirmed their faith and certainty, and have corroborated their words with actions, as Allah Almighty says: {Those are the truthful ones} [Al-Hujurat: 15]. Doubt is the absence of certainty, and certainty is a condition for the validity of faith. The Prophet, peace and blessings be upon him, said: "Whoever you meet behind this wall testifying that there is no god but Allah, being certain of it, then give him glad tidings of Paradise."

Believers are those who have affirmed Allah and His Messenger, and then did not doubt Allah's oneness and the prophethood of His Prophet. They committed themselves to obeying Allah and His Messenger and performing His obligations. As for satanic whispers, repelling and disliking them indicates faith. Their mere presence is not proof of one's faith; rather, it is the striving of the self to turn away from them.