He (Allah) has ordained for you the same religion which He ordained for Nuh, and that which We have revealed to you, and that which We ordained for Ibrahim, Musa and 'Isa saying you should establish religion and make no divisions in it. Intolerable for the idolators is that to which you call them. Allah chooses for Himself whom He wills, and guides unto Himself who turns to Him in repentance (13)And they divided not till after knowledge had come to them, through transgression between themselves. And had it not been for a Word that went forth before from your Lord for an appointed term, the matter would have been settled between them. And verily, those who were made to inherit the Scripture after them, are in grave doubt concerning it (14)

The Religion of the Messengers is One

Allah says to this Ummah:

شَرَعَ لَكُمْ مِنَ الدِّينِ مَا وَصَّىٰ بِهِ نُوحًا وَالَّذِي أَوْحَيْنَا إِلَيْكَ

(He (Allah) has ordained for you the same religion which He ordained for Nuh, and that which We have revealed to you,)

Allah mentions the first Messenger who was sent after Adam, that is, Nuh, peace be upon them, and the last of them is Muhammad ﷺ. Then He mentions those who came in between them who were the Messengers of strong will, namely Ibrahim, Musa and 'Isa bin Maryam. This Ayah mentions all five, just as they are also mentioned in the Ayah in Surat Al-Ahzab, where Allah says:

وَإِذْ أَخَذْنَا مِنَ النَّبِيِّينَ مِيثَاقَهُمْ وَمِنْكَ وَمِنْ نُوحٍ وَإِبْرَاهِيمَ وَمُوسَىٰ وَعِيسَى ابْنِ مَرْيَمَ ۖ 

(And (remember) when We took from the Prophets their covenant, and from you, and from Nuh, Ibrahim, Musa, and 'Isa son of Maryam.)(33:7). The Message which all the Messengers brought was to worship Allah Alone, with no partner or associate, as Allah says:

وَمَا أَرْسَلْنَا مِنْ قَبْلِكَ مِنْ رَسُولٍ إِلَّا نُوحِي إِلَيْهِ أَنَّهُ لَا إِلَٰهَ إِلَّا أَنَا فَاعْبُدُونِ 

(And We did not send any Messenger before you but We revealed to him (saying): None has the right to be worshipped but I, so worship Me.)(21:25). And according to a Hadith (the Prophet ﷺ said):

نَحْنُ مَعْشَرَ الْأَنْبِيَاءِ أَوْلَادُ عَلَّاتٍ، دِينُنَا وَاحِدٌ

(We Prophets are brothers and our religion is one.) In other words, the common bond between them is that Allah Alone is to be worshipped, with no partner or associate, even though their laws and ways may differ, as Allah says.

لِكُلٍّ جَعَلْنَا مِنْكُمْ شِرْعَةً وَمِنْهَاجًا ۚ 

(To each among you, We have prescribed a law and a clear way)(5:48). Allah says here:

أَنْ أَقِيمُوا الدِّينَ وَلَا تَتَفَرَّقُوا فِيهِ ۚ 

(saying you should establish religion and make no divisions in it.) meaning, Allah enjoined all the Prophets (peace and blessings of Allah be upon them all) to be as one and He forbade them to differ and be divided.

كَبُرَ عَلَى الْمُشْرِكِينَ مَا تَدْعُوهُمْ إِلَيْهِ ۚ 

(Intolerable for the idolators is that to which you call them.) means, 'it is too much for them to bear, and they hate that to which you call them, O Muhammad, i.e., Tawhid.'

اللَّهُ يَجْتَبِي إِلَيْهِ مَنْ يَشَاءُ وَيَهْدِي إِلَيْهِ مَنْ يُنِيبُ 

(Allah chooses for Himself whom He wills, and guides unto Himself who turns to Him in repentance.) means, He is the One Who decrees guidance for those who deserve it, and decrees misguidance for those who prefer it to the right path. Allah says here;

وَمَا تَفَرَّقُوا إِلَّا مِنْ بَعْدِ مَا جَاءَهُمُ الْعِلْمُ

(And they divided not till after knowledge had come to them,) means, their opposition to the truth arose after it had come to them and proof had been established against them. Nothing made them resist in this manner except their transgression and stubbornness.

وَلَوْلَا كَلِمَةٌ سَبَقَتْ مِنْ رَبِّكَ إِلَىٰ أَجَلٍ مُسَمًّى

(And had it not been for a Word that went forth before from your Lord for an appointed term,) means, were it not for the fact that Allah had already decreed that He would delay the reckoning of His servants until the Day of Resurrection, the punishment would have been hastened for them in this world.

وَإِنَّ الَّذِينَ أُورِثُوا الْكِتَابَ مِنْ بَعْدِهِمْ

(And verily, those who were made to inherit the Scripture after them,) means, the later generation which came after the earlier generation which had rejected the truth.

لَفِي شَكٍّ مِنْهُ مُرِيبٍ 

(are in grave doubt concerning it.) means, they do not have any firm conviction in matters of religion; they merely imitate their forefathers, without any evidence or proof. So they are very confused and doubtful.