When messengers visited Ibrahim's household, after a tense first encounter, they proceeded by giving him the good news of "A" (a single) son
15:53"surely we give you the good news of a boy, possessing knowledge".
The name of the boy was not directly divulged by the messengers but God informs us that it was Isaac who was meant 11:71. This was a reward from Allah for Ibrahim's patience and obedience, following the successful passing of the trial with the binding and near sacrifice of Ismail
14:39"Praise be to Allah, Who has given me in old age Ismail and Ishaq; most surely my Lord is the Hearer of prayer".
Ibrahim thanks God in this Meccan verse (almost all verses relating the stories of the prophets are Meccan) for granting him only 2 sons as a result of a prayer at a very advanced age. Ibrahim praised God for the grant of only 2 sons, and Jacob came as a nafila/addition 21:72 FROM ISAAC which is why this same verse does not mention Ismail. That is how precise the Quran is, for had it mentioned in one breath Ismail, Isaac and Jacob it would have given the impression that Jacob was Ibrahim's son but by purposefully excluding the firstborn from the list, it implies that the list of names is not meant to be about his direct sons specifically. Further, it is common in classical Arabic to speak of the grand children as coming from one's own wife in order to convey the sense of longevity of lineage 16:72.
From a linguistic point of view, it is interesting to note the intricate manner in which the Quran places words in a context. The name of Ismail is missing from the list of Ibrahim's known, righteous descendants in some verses, such as 21:72. Each context has its own peculiar reason for omitting his name and in 19:49-50, the reason transpires even more.
Ibrahim's progeny is followed by a mention of their honoring, elevating by their own people. This Meccan sura contrasts the Arabs' behavior towards their forefather Ismail with the behavior of the descendants of the Israelites towards their main prophetic figures. Although Ismail was known to the Arabs as their forefather, his spiritual path had been neglected and disfigured. He was only praised and recognized hundreds of years later when Muhammad came and restored his pure monotheistic way, honoring him. It is important noting that the stories of the biblical, and Arabian prophets are all already found in the Meccan suras. Had the prophet in Mecca, been extracting these stories from the previous traditions, he could not have passed over the central figure of Abraham and his progeny. Simply, in this period his primary addressees were the Arab pagans, who already knew of their Ishmaelite ancestry and the Kaaba's Abrahamic connection. The knowledge they lacked however was in regards to Ismail's eminence and righteousness, after centuries of baseless and prejudiced calumnies towards his character, as is amply found in Judeo-Christian traditions.
The Quran thus in this earlier period focuses on honoring Ismail by mentioning him and his virtues aside from Abraham and his known descendants 38:48,21:85,19:54. During that earlier phase the Quran paves the way (through the implicit mention of Ismail as the near-sacrifice instead of Isaac in sura 37) for a revision, in Medina, of the traditional Judeo-Christian exclusivist spiritual worldview (through the Quran's emphatic connection of Abraham to the Kaaba and the change of qibla from Jerusalem to Mecca).
This textual separation of Ismail in the Meccan chapters also points to another reality; the lack of recognition of Ismail by his people and those that followed them, as compared to the others among Ibrahim's progeny, doesnt mean that God Himself is unappreciative of his merits
19:54-55"And mention Ismail in the Book; surely he was truthful in (his) promise, and he was an apostle, a prophet. And he enjoined on his family prayer and almsgiving, and was one in whom his Lord was well pleased".
Herein lies a lesson for all times, the fact that God knows every humble person's worth regardless of that quality being exposed or not in this world, and He will manifest it and reward the person for it, sometimes in this world but always in the hereafter. It is also to be noted that the passage starting at 19:51 likewise mentions several prophets separately and prior to citing Ibrahim, including Moses, showing that the purpose isnt to establish a chronological descendency. This is further seen by the statement concluding the passage, that all previously mentioned names (Ismail, Musa, Harun etc) descend from one or more of the following
19:58"These are they on whom Allah bestowed favors, from among the prophets OF the seed of Adam, and OF those whom We carried with Nuh, and OF the seed of Ibrahim and Israel, and OF those whom We guided and chose".
When verses such as 19:49 speak of Allah giving/wahabna Jacob to Ibrahim that giving does not only signify the giving of a son, for of Moses it is said a few verses further on,
19:53"We gave him his brother Aaron, a prophet"
though Aaron was older than Moses and his brother 20:94,28:34.
It literally means the giving without taking, implying making a favor. Also, in 2:133 Jacob, in a context where he is stressing to his progeny the universality of his forefathers' religion (see 12:38), Jacob is quoted as praising his "fathers" Ibrahim and Ismail and Ishaq. The often mention of Jacob among Ibrahim's descendants is done as a reminder of God favoring Ibrahim with a righteous posterity, even among his grandchildren, and Jacob was a grand child whom Ibrahim particularly affectioned. Ibrahim is quoted as including him in principle among his own sons when issuing his final spiritual instructions, although the Quran, in introduction to the quote, separates between Jacob and Ibrahim's direct progeny
2:132"And Ibrahim instructed his sons AND Yaqoub: O my sons! Indeed, Allah has chosen for you the religion, so do not die except while you are submitters".
Hebrew scriptures on the other hand are oddly silent on Abraham's relationship with his own sons after Isaac's marriage to Rebecca. Contrary to the above Quran verse depicting his affection for his grandchildren, the HB says nothing about that part of his life. This is odd considering that he lived 175 years and was 100 when Isaac was born. Isaac married when he was 40. 20 years later, when he was 60, his twins Esau and Jacob were born Gen21:5,25:7. Abraham had thus lived on 15 years after his grandchildren's birth. For a scripture that spends chapters and long passages listing useless names of people and places and genealogies, to omit any mention of how the main patriarchs interacted is strange.
Only the muddled way in which Torah was transmitted can explain this neglect, from various sources containing different informations. For example Abraham's death is recorded in Gen25:8 and yet the birth of his grandchildren comes later on, thus contradicting the above data.
Then addressing Ibrahim's wife, the messengers
11:71"gave her the good news of Ishaq and after Ishaq of Yaqoub".
Sarah was not only told that she would give birth, but also that her progeny will continue and this verse makes it clear that Jacob would come from Isaac, not from her
11:72"shall I bear "A" (a single) son.."
which echoes
15:53"the good news of "A" (a single) boy"
given moments before to Ibrahim.
As was said concerning Ibrahim earlier, the text does not necessarily imply that Sara was informed of her future child's name. The verse 11:71 isnt a direct quote of the discussion that occured between her and the messengers, it is God informing us retrospectively of whom the messengers meant when they announced the birth of a child, followed by another. It can also be added that since no direct naming occured, the messengers were not concerned by citing all the great names among Sara's progeny (hence the stop at Jacob), just to establish that she would bear a child and that her progeny would carry on fruitfully, which is a reassurance and satisfaction, especially considering Sara's very late impregnation.
In contrast to his wife, Ibrahim's initial reaction to the good news was an astonishing reiteration of it as he knew that from the point of the natural laws, the birth of such a child by him was a remote matter
15:54"Do you give me this good news in my old age?".
But from God's point, who had already displayed many miracles to him such as the manner in which he was saved from his people, and who in addition had already granted him a firstborn at an old age, Ibrahim knew it was a possibility. So could it hopefully be that this good news is from God, or was it from them
"Of what do you give me good news".
This is followed by a reassuring confirmation by the messengers 15:55 and a rhetorical question by Ibrahim
15:56"He said: And who despairs of the mercy of his Lord but the erring ones?"
This implies "I am not of the erring-ones who despair of God's mercy and if this news is truly from God then I believe it". Ibrahim's wife on the other hand, because she had despaired of one day conceiving, was overcome by grief because she thought that even to God, the realization of such a thing would be far off
11:72"This is a strange thing indeed".
But she was reassured while at the same time rebuked for her skepticism
11:73"Do you deem Allah's command a strange thing? The mercy of Allah and His blessings are on you, O people of the house, surely He is Praised, Glorious".
The name "Isaac" implies laughter, out of joy or mockery, but the name is connected in the HB to Ibrahim's rejoicing and believing the good news of Isaac's birth, reacting with questions which are positive assertions Gen17:17. The name is not related to Sarah's laughter who did not believe and ridiculed, which actually displeased God and caused her, out of fear, to lie and deny having laughed at the news Gen18:12-15.
Both Ishmael, implying divine acceptance of prayers, and Isaac, implying laughter, are names connected to Ibrahim who, at an advanced age, dearly prayed God for a first born and rejoiced at the news of a second son
14:39"Praise be to Allah, Who has given me in old age Ismail and Ishaq; most surely my Lord is the Hearer of prayer".
The circumstances of Isaac's birth thus definitely have a place and purpose in the Quran narrative, as it depicts him as a reward, a pleasant and joyful news to Ibrahim following Ismail's near-sacrifice.
It isnt the case with Ismail. To the Quran narrative, the relevant points in regards to Ismail are his connection to the Kaaba, his early settlement in Mecca, and the incident of his near sacrifice 2:124-131,14:35-41,37:99-113. That is why no mention is made of his mother either. The only thing related as regards his birth is that he was given to Ibrahim at a very old age, as a favor and in answer to Ibrahim's prayers, which parallels with the account in the HB.
So although the existence of a second wife to Ibrahim isnt explicitly mentioned it certainly can be inferred that Ismail and Isaac came from different wives of Ibrahim. As was already stated, Isaac's mother received the good news of a single son and was incredulous that her husband, at an old age, would be able to impregnate her. Yet Ibrahim had already done so once before, per 14:39 above (see in connection with 37:99-113 which was revealed earlier chronologically). Had this occured with her she wouldn't have been sceptical that it could happen again. Even the angelic announcement of a pregnancy to her, sounds like a first-time experience.
Neither could it be that the same woman had Ismail at a young age and that Isaac miraculously came to her later at an age where she wouldnt normally conceive. The verse 11:72 implies that the age gap between Ibrahim and the mother of Isaac is relatively small and according to Ibrahim's words in 14:39, both Ismail and Isaac were given to him at an old age which also means that Isaac's mother must have also been old when both sons were born in case they were both her sons.
Finally the Bible itself corroborates that the age gap between Abraham and Sarah was 30 years, and Ishmael was born when Abraham was 90, meaning Sarah was approx 60, which is beyond the menopausal age.
Further reading answering Sam Shamoun "Is The Quran God’s Word? Pt. 1"
