Tafsir of Al-Anbiya' 21:55

"They said, 'Have you brought us the truth...'"

They remained astonished at his labeling them as misguided. They assumed that what he had said was spoken in jest and playfulness, not in earnest. So they said to him: "This which you have brought us, is it serious and true, or is it play and jest?"

{He said, "Nay, your Lord is the Lord of the heavens and the earth, who created them, and I am of those who bear witness to that."}