قَيِّمًا لِيُنْذِرَ بَأْسًا شَدِيدًا مِنْ لَدُنْهُ وَيُبَشِّرَ الْمُؤْمِنِينَ الَّذِينَ يَعْمَلُونَ الصَّالِحَاتِ أَنَّ لَهُمْ أَجْرًا حَسَنًا ﴿۲﴾ مَاكِثِينَ فِيهِ أَبَدًا ﴿۳﴾ وَيُنْذِرَ الَّذِينَ قَالُوا اتَّخَذَ اللَّهُ وَلَدًا ﴿۴﴾ مَا لَهُمْ بِهِ مِنْ عِلْمٍ وَلَا لِآبَائِهِمْ كَبُرَتْ كَلِمَةً تَخْرُجُ مِنْ أَفْوَاهِهِمْ إِنْ يَقُولُونَ إِلَّا كَذِبًا ﴿۵﴾ فَلَعَلَّكَ بَاخِعٌ نَفْسَكَ عَلَى آثَارِهِمْ إِنْ لَمْ يُؤْمِنُوا بِهَذَا الْحَدِيثِ أَسَفًا ﴿۶﴾

﴾2﴿ Qaiyimal liyunzira ba'asan shadeedam mil ladunhu wa yubashshiral mu'mineenal lazeena ya'maloonas saalihaati anna lahum ajran hasanaa
﴾3﴿ Maakiseena feehi abadaa
﴾4﴿ Wa yunziral lazeena qaalut takhazal laahu waladaa
﴾5﴿ Maa lahum bihee min 'ilminw wa laa li aabaaa'ihim; kaburat kalimatan takhruju min afwaahihim; iny yaqooloona illaa kazibaa
﴾6﴿ Fala'allaka baakhi'un nafsaka 'alaaa aasaarihim illam yu'minoo bihaazal hadeesi asafaa

﴾2﴿ Straightforward in its guidance, to warn of a severe punishment that comes from Him, and to give glad tidings to the believers—those who perform deeds in accordance with the Sunnah and divine guidance—that indeed, they will have a good reward
﴾3﴿ To dwell therein forever
﴾4﴿ And to warn those who say that Allah, the Exalted, has taken a son
﴾5﴿ They have no knowledge of this, nor did their forefathers. Grave is the word that comes out of their mouths; they speak nothing but a lie
﴾6﴿ So, will you kill yourself with grief over them if they do not believe in this word (Tawhid) out of sorrow

[2] (Qayyiman) means it contains firm messages—it strengthens monotheism with solid proofs and fortifies the believer in their monotheism. The verse also mentions the wisdom behind the revelation of the Qur'an: warning and giving glad tidings.
For warning (indhār), three elements are necessary: the warner (mundhir), those being warned (mundhar lahum), and that which they are warned about (mundhar ‘anhu).
Thus, in the pronoun "li-yundhira"—which refers either to the Book or the servant (Prophet)—there is a reference to the warner. Alongside "ba’san shadīdan" (severe punishment), the thing being warned about (mundhar ‘anhu) is mentioned.
Those being warned (mundhar lahum) are mentioned afterward.
In the pronoun "yubashir" (gives glad tidings), there is a reference to the bearer of good news (mubashshir), which is either the Book or the servant. Along with "al-mu’minīn", those receiving the glad tidings (mubashshar lahum) are mentioned.
With "anna lahum ajran hasanan" (that they will have a good reward), the content of the glad tidings (mubashshar bihi) is mentioned.
This verse includes both warning and glad tidings.
[3] This pertains to the glad tidings and is a reference to the eternal nature of Paradise.
[4] In this verse, those being warned (mundhar lahum) are mentioned—and it alludes to the fact that the Qur'an aims to refute those who believe in the adoption of a child (by Allah).
What is meant by "child" (walad) here is that the polytheists affirm a being to whom they attribute a portion of Allah's exclusive attributes, such that signs of divinity become manifest in that being.
For this reason, they consider worshipping that being necessary and believe it fulfills needs—just as, in a child, the traits of the parent are manifest, and the child acts as the parent’s representative.
[5] In this verse, the condemnation of this belief is mentioned—that this statement is without any evidence, and the very lack of proof is enough to demonstrate the ugliness of such a belief or claim.
They merely imitate their forefathers. Then, a potential objection arises: even if there’s no proof for this statement, what harm is there? It’s just a common saying, nothing serious.
So the response is given: “Kaburat kalimatan takhruju min afwahihim”—this statement is extremely grave and ugly, coming out of their insignificant mouths without any proof.
The reason for its repulsiveness is then stated: “In yaqūlūna illā kadhībā”—they say nothing but a lie.
[6] In this, there is consolation for the Prophet (May Allah bless him and give him peace)—that he should not grieve excessively over the denial of these rejecters, to the point of destroying himself out of sorrow.
The word "la‘alla" here is for rhetorical questioning (istifhām inkārī), and similar usage appears in verse 3 of Surah Ash-Shu‘arā and verse 8 of Surah Fāṭir as well.