And never be of those who deny the signs of Allāh and [thus] be among the losers.1
Translation: Saheeh International (English)
1 Among the interpretations of the last two verses is that they were meant to stir the Prophet (ﷺ) to declare and confirm his certainty, which he did. Another is that although the words are addressed to the Prophet (ﷺ), they are directed to all people.
Do not be of those who deny Allah’s proof and evidence, because that will make you one of those who have lost their own souls by bringing them to the point of destruction because of their disbelief. All these warnings are meant to show the seriousness of doubt and denial, despite the fact that the Prophet is protected from such things.