Tafsir of Al-Hijr 15:55

"They said, 'We have given you good tidings in truth...'"

(Meaning: With a matter that is inevitably realized, or with certainty that has no ambiguity, or in a manner that is true. It is a matter from the One who possesses command, who is capable of creating a child without parents; how then is it difficult to bring one into existence from an old man and an old woman?)

"...so do not be of the despairing."

(Meaning: Do not be among those who despair of the breaking of the norm for your sake. The manifestation of miracles at the hands of the Prophets—peace be upon them—is frequent, to the point that it is not considered, in relation to them, a violation of the norm. It is as if his intention—peace be upon him—was to magnify the blessing of the Almighty upon him, within the context of the natural astonishment based upon the customary path of Allah—the Exalted—among His servants, not the deeming of it as far-fetched in relation to the Power of the Majestic—His Majesty is supreme. For he—peace be upon him—or rather, a Prophet absolutely, is too lofty in status for that. This is indicated by the statement of the angels—peace be upon them—"So do not be of the despairing," with all the hyperbole it contains, rather than them saying, "from those who doubt," or the like.)