وَ السَّمَآءِ ذَاتِ الرَّجْعِ ﴿ۙ۱۱﴾

  By heaven from which rain pours down,


 وَ الْاَرْضِ ذَاتِ الصَّدْعِ ﴿ۙ۱۲﴾

  And the earth that splits thereof.


 اِنَّہٗ لَقَوْلٌ فَصْلٌ ﴿ۙ۱۳﴾

  Undoubtedly, Quran is necessarily a decisive word.


 وَّ مَا ہُوَ بِالْہَزْلِ ﴿ؕ۱۴﴾

  And it is no merriment.

Tafsir al-Kabeer                                                                                                             التفسیر الکبیر                        

أَيِ الْقُرْآنُ فَاصِلٌ بَيْنَ الْحَقِّ وَالْبَاطِلِ كَمَا قِيلَ: لَهُ فُرْقَانٌ

i.e. the Holy Quran is the Judge between truth and falsehood, as it is also called Al-Furqaan (The Judge).

Tafsir al-Kabeer (Mafateeh al-Ghaib) of Imam Fakhruddin Muhammad ibn Umar al-Raazi al-Shafe’i t D. 606 A.H.

Tafsir al-Qurtubi                                                                                                                                                                                      تفسیر القرطبی                                                    

رَوَاهُ الْحَارِثِ عَنْ عَلِيٍّ رَضِيَ اللَّهُ عَنْهُ قَالَ: سَمِعْتُ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَقُولُ: كِتَابٌ فِيهِ خَبَرُ مَا قَبْلَكُمْ وَحُكْمُ مَا بَعْدَكُمْ، هُوَ الْفَصْلُ، لَيْسَ بِالْهَزْلِ، مَنْ تَرَكَهُ مِنْ جَبَّارٍ قَصَمَهُ اللَّهُ، وَمَنَ ابْتَغَى الْهُدَى فِي غَيْرِهِ أَضَلَّهُ اللَّهُ

Sayyiduna Harith – may Allah be pleased with him – narrated it from Sayyiduna ‘Ali – may Allah be pleased with him:  I heard the Messenger of Allah – may Allah be pleased with him – saying, “It is the book that contains the news of people who were before you and the account of those who will follow you.  It is the judge and it is no merriment.  Whoever abandons it and turns to oppression Allah Almighty punishes him.  One who seeks guidance other than from it, Allah Almighty leads him astray.

Tafsir Qurtubi (Al-Jame’ Li Ahkaam al-Quran) Imam Shamsuddin Muhammad ibn Ahmad al-Qurtubi t D. 671 A.H.

Tafsir al-Jalalain                                                                                                                        تفسیر الجلالین                                                

{وَالسَّمَاء ذَات الرَّجْع} الْمَطَر لِعَوْدِهِ كُلّ حِين

 {وَالْأَرْض ذَات الصَّدْع} الشَّقّ عَنْ النَّبَات

 {إِنَّهُ} أَيْ الْقُرْآن {لَقَوْل فَصْل} يَفْصِل بَيْن الْحَقّ والباطل

 {وَمَا هُوَ بِالْهَزْلِ} بِاللَّعِبِ وَالْبَاطِل

By the heaven of returns, [of] the rain that returns time and again,

And [by] the earth of fissures, splitting with [the growth of] vegetation,

Assuredly it, the Qur’ān, is a decisive word, distinguishing between truth and falsehood

And it is not a jest, frivolity or falsehood.

Tafsir al-Jalalain of Imam Jalaaluddin Muhammad ibn Ahmad al-Mahalli al-Shafe’i t D. 864 A.H. and Imam Jalaaluddin Abd al-Rahman ibn Abi Bakr al-Suyooti al-Shafe’i t D. 911 A.H.