Abbas - Tanwîr al-Miqbâs min Tafsîr Ibn ‘Abbâs
Allah then mentions their argument with the Prophet (pbuh) about the Religion of Islam, saying: (And if they) i.e. the Jews and Christians (argue with thee, O Muhammad, say: I have surrendered my purpose) I make my Religion and works sincere (to Allah and (so have) those who follow me. And say unto those who have received the Scripture) the Jews and Christians (and those who read not) i.e. the Arabs: (Have ye (too) surrendered?) do you surrender as we have surrendered? Allah then said: (If they surrender) as you have surrendered, (then truly they are rightly guided) from error, (and if they turn away) from surrender, (then it is your duty only to convey the message (unto them)) on behalf of Allah. (Allah is Seer of (His) bondmen) those who believe and those who do not.
So if they, the disbelievers, dispute with you, O Muhammad (s), concerning religion, say, to them: ‘I have surrendered my countenance to God, [that is to say] I have submitted to Him, I, and whoever follows me’ (wajh, ‘countenance’, is chosen here because of its noble character, for the other [parts of the body] will just as soon [surrender once the countenance has]); and say to those who have been given the Scripture, the Jews and the Christians, and to the uninstructed, the Arab idolaters: ‘Have you submitted?’, that is to say, ‘Submit!’ And so if they have submitted, they have been guided, from error, but if they turn their backs, to Islam, your duty is only to deliver, the Message; and God sees His servants, and so requites them for their deeds — this [statement] was [revealed] before the command to fight [them] had been revealed.
Allah bears witness, and verily, Allah is sufficient as a Witness, and He is the Most Truthful and Just Witness there is; His statement is the absolute truth,
أَنَّهُ لاَ إِلَـهَ إِلاَّ هُوَ
(that La ilaha illa Huwa) meaning, He Alone is the Lord and God of all creation; everyone and everything are His servants, creation and in need of Him. Allah is the Most Rich, Free from needing anyone or anything. Allah said in another Ayah,
لَّـكِنِ اللَّهُ يَشْهَدُ بِمَآ أَنزَلَ إِلَيْكَ
(But Allah bears witness to that which He has sent down (the Qur'an) unto you (O Muhammad )) 4:166.
Allah then mentioned the testimony of His angels and those who have knowledge after he mentioned His own testimony,
(Allah bears witness that none has the right to be worshipped but He), and the angels, and those having knowledge (also bear witness to this)). This Ayah emphasizes the great virtue of those who have knowledge.
((He) maintains His creation in justice) in all that He does,
لاَ إِلَـهَ إِلاَّ هُوَ
(None has the right to be worshipped but He) thus emphasizing this fact,
(the Almighty, the All-Wise.) the Mighty that does not submit to weakness due to His might and greatness, the Wise in all His statements, actions, legislation and decrees.
The Religion with Allah is Islam
إِنَّ الدِّينَ عِندَ اللَّهِ الإِسْلَـمُ
(Truly, the religion with Allah is Islam.) Allah states that there is no religion accepted with Him from any person, except Islam. Islam includes obeying all of the Messengers until Muhammad who finalized their commission, thus closing all paths to Allah except through Muhammad. Therefore, after Allah sent Muhammad, whoever meets Allah following a path other than Muhammad's, it will not be accepted of him. In another Ayah, Allah said,
(And whoever seeks a religion other than Islam, it will never be accepted of him) 3:85.
In this Ayah 3:19, Allah said, asserting that the only religion accepted with Him is Islam,
إِنَّ الدِّينَ عِندَ اللَّهِ الإِسْلَـمُ
(Truly, the religion with Allah is Islam.)
Allah then states that those who were given the Scripture beforehand divided in the religion after Allah sent the Messengers and revealed the Books to them providing them the necessary proofs to not do so. Allah said,
(Those who were given the Scripture (Jews and Christians) did not differ except out of rivalry, after knowledge had come to them.) meaning, some of them wronged others. Therefore, they differed over the truth, out of envy, hatred and enmity for each other. This hatred made some of them defy those whom they hated even if they were correct. Allah then said,
وَمَن يَكْفُرْ بِآيَـتِ اللَّهِ
(And whoever disbelieves in the Ayat of Allah) meaning, whoever rejects what Allah sent down in His Book,
فَإِنَّ اللَّهِ سَرِيعُ الْحِسَابِ
(then surely, Allah is Swift in reckoning.) Allah will punish him for his rejection, reckon him for his denial, and torment him for defying His Book. Thereafter, Allah said.
(So if they dispute with you (Muhammad )) so if they argue with you about Tawhid,
(And say to those who were given the Scripture (Jews and Christians) and to those who are illiterates (Arab pagans): "Do you (also) submit yourselves'' If they do, they are rightly guided; but if they turn away, your duty is only to convey the Message.) meaning, their reckoning is with Allah and their return and final destination is to Him. It is He Who guides whom He wills and allows whom He wills to stray, and He has the perfect wisdom and the unequivocal proof for all of this. This is why Allah said,
وَاللَّهُ بَصِيرٌ بِالْعِبَادِ
(And Allah sees the servants.) for He has perfect knowledge of who deserves to be guided and who does not deserve to be guided. Verily,
لاَ يُسْأَلُ عَمَّا يَفْعَلُ وَهُمْ يُسْـَلُونَ
(He cannot be questioned for what He does, while they will be questioned.) 21:23 because of His perfect wisdom and mercy. This and similar Ayat are clear proofs that the Message of Muhammad is universal to all creation, as it is well established in the religion, according to the various texts of the Book and Sunnah. For instance, Allah said,
(Blessed be He Who sent down the criterion to His servant that he may be a warner to the `Alamin (mankind and Jinn).) 25:1.
The Two Sahihs and other collections of Hadith recorded that the Prophet sent letters to the kings of the earth during his time and to different peoples, Arabs and non-Arabs, People of the Book and the unlettered, just as Allah had commanded him. `Abdur-Razzaq recorded that Ma`mar said, that Hammam said that Abu Hurayrah said that the Prophet said,
(By He in Whose Hand is my soul! No member of this Ummah, no Jew or Christian, hears of me but dies without believing in what I was sent with, but will be among the people of the Fire.) Muslim recorded this Hadith.
(A Prophet used to be sent to his people, but I was sent to all mankind.)
Maududi - Sayyid Abul Ala Maududi - Tafhim al-Qur'an
It implies that in the sight of Allah there is only one correct system and one right way of life for man. It is this: Man should worship Allah, acknowledge Him as his Master and surrender himself completely to Him in His worship and service. He should not invent his own way of worship but should faithfully follow that Guidance alone which Allah has revealed through His Messengers, without adding anything to or taking away anything from it. This way of thinking and behaving is called "Islam." And it is the absolute right of the Creator and the Master of the Universe that He should not accept as lawful from His subjects, His own creation, any way other than Islam. One might ignorantly think it to be one's right to follow any system, atheism, idolatry, etc., but the Ruler of the Universe will regard this behaviour as rebellious.
It means that originally Islam and Islam alone was professed and preached by every Messenger who was sent by Allah at any time in any comer of the world. Hence any Scripture sent down to any community in any language taught the same Islam. Afterwards, the people distorted this original religion and added to it something to suit their interests or to gratify their lusts, and omitted those things from it which went against their interests. They invented new religions just because they wanted to transgress the prescribed limits and run after undue privileges and gains and distinctions. Thus they made changes in the beliefs, principles and injunctions of the true Faith to make it subservient to their own desires and lusts.
The same thing may be expressed thus: "My followers and I have been convinced of this same pure Islam and have accepted the true religion of Allah; now tell us whether you also will give up the innovations which you and your elders have introduced into it and turn to the original true religion."
So if they dispute with you say: “I have surrendered my countenance to God and whoever follows me”: and say to those who have been given the scripture and to the uninstructed: “Have you submittedḍ” And so if they have submitted they have been guided but if they turn their backs your duty is only to deliver; and God sees His servants. “Look at them through the eye of [God's] free disposal taṣrīf so that your state does not become unsettled at the differences and the disparity of their stages. One who looks at created beings through the eye of [God's] deliberative power qudra knows that the One who determines for all based on what He has chosen for each is One. Call them publicly when in public and bear witness privately to Our free disposal taṣrīf with regard to them when in private.” Occupy your tongue by counseling them but empty your heart of their talk and separate your innermost self from witnessing them for We have not charged you with their affairs [but only] with deliver[ing] [the message]. The One who brings about affairs and originates is Us.”