Tafsir of Al-Qalam 68:2

You, by the grace of your Lord, are not insane. meaning -- and all praise is due to Allah -- `you are not crazy as the ignorant among your people claim. They are those who deny the guidance and the clear truth that you have come with. Therefore, they attribute madness to you because of it.'

وإن لك ﻻإجرا غير ممنون