Tafsir of As-Saffat 37:101

It is evident that the subject of the glad tidings is the very same one he had requested [as a gift], and such phrasing is conventionally only used regarding children. The statement comprises the glad tidings that he is a male, as the word ghulam (boy) is specific to that; that he would reach adulthood, or that the "reaching" refers to the known age of maturity, for it is a requirement of describing him as halim (forbearing), since forbearance is characteristic of that age according to custom. Rarely does one find in young children breadth of heart, excellent patience, and overlooking in every matter.

It is also possible that this is understood from the words of the Exalted, "(a) boy," for it may specifically refer to the time after puberty, even if it is used in a general sense; and upon this is the custom, as mentioned by the jurists. That he would be halim—and what forbearance is like his forbearance? His father presented him with the command of slaughter, and he said: "You will find me, if Allah wills, among the patient." So, what do you suppose of him after he reached maturity?

It has been said: Allah the Exalted did not describe any prophet with hilm (forbearance) due to the rarity of its existence, except for Ibrahim and his son, peace be upon them both. Their state, mentioned hereafter, serves as proof of what has been stated regarding them.