So We gave him the glad tidings of a forbearing boy.
This child was Ismail, peace be upon him, for he was the first child of whom glad tidings were given to Ibrahim, peace be upon him, and he was older than Ishaq.
The Muslims and the People of the Book agree, and indeed it is stated in their Book, that Ismail, peace be upon him, was born when Ibrahim, peace be upon him, was eighty-six years old, and Ishaq was born when Ibrahim was ninety-nine years old.
According to their Book, Allah commanded Ibrahim to sacrifice his only son, and in another text it says his firstborn son. But here they falsely inserted the name of Ishaq. This is not right because it goes against what their own Scripture says.
They inserted the name of Ishaq because he is their ancestor, while Ismail is the ancestor of the Arabs. They were jealous of them, so they added this idea and changed the meaning of the phrase "only son" to mean `the only son who is with you,' because Ismail had been taken with his mother to Makkah. But this is a case of falsification and distortion, because the words "only son" cannot be said except in the case of one who has no other son. Furthermore, the firstborn son has a special status that is not shared by subsequent children, so the command to sacrifice him is a more exquisite test