Indeed, Allah does not forgive associating others with Him ˹in worship˺, but forgives anything else of whoever He wills. And whoever associates others with Allah has indeed committed a grave sin.4:48
It literally says that everything can be forgiven except polytheism. So the Jews can also be forgiven? After all, they believe in the one and only God.
And about atheists: it is clear that atheists cannot be forgiven, but why are they not mentioned in this verse?
The Jews and atheists are disbelievers, as they commit Kufr. The Jews disbelieve in Allah's revelations (Injeel, Quran) and prophets (Zechariah, John, Jesus and Muhammad ﷺ) as well as in many other creeds regarding Allah's person (such as claiming that He rested on the Sabbath). While the atheists disbelieve in Allah completely.
There are numerous verses in the Quran which say or mean that the disbelievers will not be forgiven by Allah:
فلن يغفر الله لهم ذلك بأنهم كفروا بالله ورسوله
Never will Allah forgive them. That is because they disbelieved in Allah and His Messenger.
إن الذين كفروا وماتوا وهم كفار أولئك عليهم لعنة الله والملائكة والناس أجمعين خالدين فيها لا يخفف عنهم العذاب ولا هم ينظرون
Indeed, those who disbelieve and die while they are disbelievers - upon them will be the curse of Allah and of the angels and the people, all together. Abiding eternally therein. The punishment will not be lightened for them, nor will they be reprieved.
And Jews and atheists come under the meaning of these verses, as they have disbelieved.
As for the verse:
إن الله لا يغفر أن يشرك به ويغفر ما دون ذلك لمن يشاء
Indeed, Allah does not forgive association with Him, but He forgives what is less than that for whom He wills.
— Quran 4:48 and Quran 4:116
It does not say 'polytheism' but rather it says أن يشرك به i.e. shirk. While shirk is often translated simply as polytheism, it is not limited to that.
Rather, as a term shirk is often used as a synonym for kufr in Islamic texts, as mentioned by various scholars:
الشرك والكفر قد يطلقان بمعنى واحد وهو الكفر بالله
Kufr and Shirk may carry the same meaning, which is disbelief in Allah
كل كفر شرك، وكل شرك كفر
Every Kufr is Shirk, and every Shirk is Kufr
كل كافر مشرك بالله لأن الكافر إذا كفر بنبي فقد زعم أن الآيات التي أتى بها ليست من عند الله، فيجعل ما لا يكون إلا لله لغير الله
Every Kafir is a Mushrik, for one who disbelieves in a prophet holds that the verses (signs) given to him are not from Allah, hence he ascribes an exclusive act of Allah to other than Allah
Also see Qamoos al-Muheet, Misbaah al-Muneer , Taaj al-‘Aroos etc. Some have also explained that kufr is shirk because it is essentially taking one's own whims as a god besides Allah (see 25:43).
There are examples within the Quran and Ahadith where shirk and mushrik are used for Kufr rather than self-admitted polytheism:
Consider the following verse:
ولا تأكلوا مما لم يذكر اسم الله عليه وإنه لفسق وإن الشياطين ليوحون إلى أوليائهم ليجادلوكم وإن أطعتموهم إنكم لمشركون
And do not eat of that upon which the name of Allah has not been mentioned, for indeed, it is grave disobedience. And indeed do the devils inspire their allies [among men] to dispute with you. And if you were to obey them, indeed, you would be associators [of others with Him].
This verse was revealed when some of the Quraysh argued with the Muslims saying that it was lawful to eat dead meat (carrion). They argued that the Muslims eat what they kill themselves and what their own hunting dogs and hawks kill - so they should also eat what Allah Himself kills (i.e. animals which die naturally). This verse says that if we were to obey them (i.e. consider carrion to be lawful) then we would become Mushrikeen (i.e. would commit shirk). And it is obvious that considering carrion to be lawful is not polytheism but rather it is Kufr. And it is called Shirk even though the person will not admit to belief in multiple deities.
Also consider the hadith:
بين الرجل وبين الشرك والكفر ترك الصلاة
Between a man and Shirk and Kufr there stands his giving up the Salat
— Muslim
It is obvious that abandoning salah (i.e. not considering it obligatory) is Kufr, and it is called Shirk even though the person does not express belief in multiple deities.
And there are examples within the Quran and Ahadith where mushrik is used for Jews. For example consider the verse 2:135 - it is apparent that here Mushrikeen means all disbelievers and especially the intent is to say that Abraham was not a Jew or Christian. And it is also understood in this, this and this hadith that Jews are being referred to by calling them Mushrikeen. And scholars too will often in their writings refer to the Jews as Mushrikeen such as here.
Hence, 4:48 means that Allah will not forgive any Kufr: be it denial of the existence of Allah, or denial of any belief regarding Allah such as Tawheed, or denial of His prophets and revelations etc.
The fact that the Jews and Christians are never forgiven and stay in Hell is evident in the Quran, Sunnah, and consensus. Allah says:
Indeed, those who disbelieve and commit wrong [or injustice] - never will Allah forgive them, nor will He guide them to a path.
Except the path of Hell; they will abide therein forever. And that, for Allah, is [always] easy. (4:168-169)
So, eternal punishment is generalized for all those who disbelieve including the Jews and Christians.
The fact that everyone agrees Jews are not saved indicates to us that Jews fall into shirk according to the Sharia. But, they do not fall into shirk in the linguistic sense, and that is why Allah separates them from the mushrikeen in other places of the Quran.
In the religious terminology, kufr and shirk are synonymous.
Another indication of this is the fact that the context of this verse 4:48 is a discussion with the Jews, and if they did not fall into shirk, that wouldn't make sense.
The verses:
O you who were given the Scripture, believe in what We have sent down [to Muhammad], confirming that which is with you, before We obliterate faces and turn them toward their backs or curse them as We cursed the sabbath-breakers. And ever is the decree of Allah accomplished.
Indeed, Allah does not forgive association with Him, but He forgives what is less than that for whom He wills. And he who associates others with Allah has certainly fabricated a tremendous sin. (4:47-48)
Why the Jews are considered as falling into shirk in the Sharia could be due to one of the following reasons:
They preferred to stick to their own law instead of following the law Allah revealed in Islam. Hence, they associated their own legislation to Allah. See:
They have taken their scholars and monks as lords besides Allah, and [also] the Messiah, the son of Mary. And they were not commanded except to worship one God; there is no deity except Him. Exalted is He above whatever they associate with Him. (9:31)
Although the Jews did not worship their scholars, their sticking to their legislation and believing in it over what Allah revealed is considered them taking lords besides Allah.
Since they follow a false religion, when they worship, it is like they are worshiping Shaitan. Also see:
Did I not enjoin upon you, O children of Adam, that you not worship Satan - [for] indeed, he is to you a clear enemy - And that you worship [only] Me? This is a straight path. (36:60-61)
They call upon instead of Him none but female [deities], and they [actually] call upon none but a rebellious Satan. (4:117)
Even though no one deliberately worships Shaitan, their following of a religion that Shaitan invited to and worshiping how and whom Shaitan asked them to worship is considered shirk.
And Allah knows best.
