In The Name of Allaah, The Most Merciful, The Bestower of Mercy.
Imaam As-Sadi [may Allaah have mercy upon him] said:
It (i.e. Islam) is the great and decisive religion- decisive in all its rulings and reports. Neither does it report except based on truth and that which absolutely addresses the reality of a situation, nor does it pass a judgement except with (perfect) truth and justice. Neither is there any true knowledge that invalidates any of its reports nor is there any ruling better than its rulings. Its fundamentals, its rules by way of which judgement is passed on various subject matters and its foundations perfectly address and regulate all affairs – past and present. Perfect equity and justice, mercy, goodness and benevolence are applied wherever the various mutual dealings between individuals and groups are established- in every time and place – based on its fundamental principles, because it is a revelation from the All-Wise, The One Worthy of all Praise (Allaah).
Allaah said: [كتاب أحكمت آياته ثم فصلت من لدن حكيم خبير – (This is) a Book (i.e. the Qur’aan), the Verses whereof are perfected (in every sphere of knowledge, etc.), and then explained in detail from One (Allah), Who is All-Wise and Well-Acquainted (with all things)]. [Surah Hud Aayah 1]
Allaah said: [لا يأتيه الباطل من بين يديه ولا من خلفه تنزيل من حكيم حميد – Falsehood cannot come to it from before it or behind it (it is) sent down by the All-Wise, Worthy of all praise (Allah)]. [Surah Fussilat. Aayah 42]
Allaah said: [إنا نحن نزلنا الذكر وإنا له لحافظون – Verily We: It is We Who have sent down the reminder r (i.e. the Qur’an) and surely, We will guard it (from corruption)]. [Surah Al-Hijr. Aayah 9]
Its words are certainly protected against addition, deficiency and alteration, and its rulings are safeguarded from deviation and deficiency; rather they are at the highest level of justice, uprightness and a means of facilitating every good.
Commentary: The decisiveness of this religion is related to both reports and commands. All its reports are based on absolute truthfulness and all its commands are based on (perfect) justice. There is no sound knowledge that belies the reports of the Qur’aan nor any sound knowledge that nullifies its rulings, and there is no era in which its reports and rulings are belied (i.e. there can be nothing based on evidence to belie its rulings). Allaah is the Creator of the creation and He alone knows what is good for them and what will lead them to success. (see footnote a) [From 34mins 20secs to 39mins 02secs. https://www.al-badr.net/detail/8LD6UgwQrZ paraphrased excerpt]
Footnote a: In another treatise of Imaam As-Sadi titled: Dalaa’il Al-Qur’aaniyyah Fee Anna Al-Uloom Wal-A’maal An-Naafi’ah al-Asriyyah Daakhilatun Fee Ad-Deen Al-Islaamiy, he stated: Allaah said: [وَٱللَّهُ يَقُولُ ٱلۡحَقَّ وَهُوَ يَهۡدِى ٱلسَّبِيلَ – Allah says the truth, and He guides to the (Right) Way]. [Surah Al-Ahzaab. Aayah 4]
This noble verse makes it explicitly clear that Allah [The Exalted] says the truth- truthfulness and certainty in His reports, perfect justice and wisdom in His commands and prohibitions. Everything He has stated is absolute truth and a fact that conforms to true reality; beneficial for the servants as a means of rectifying their creed, manners, religion and worldly affairs. Everything He has commanded is righteousness, goodness, benevolence, a perfect benefit and a blessing; and everything He has forbidden is evil, harm and corruption, and this relates to both religious and worldly affairs. The entire Islamic legislation is a detail explanation and clarification of this mighty fundamental principle that has been stated in this verse and other than it. Then Allāh said: [وَهُوَ يَهۡدِى ٱلسَّبِيلَ – and He guides to the (Right) Way]- Meaning, the path that leads to the truth through which Allaah judges. So, Allah took it upon himself that He must explain and clarify this wholesome truth through manifest intellectual and textual proofs, as He said in another verse: [سَنُرِيهِمۡ ءَايَـٰتِنَا فِى ٱلۡأَفَاقِ وَفِىٓ أَنفُسِہِمۡ حَتَّىٰ يَتَبَيَّنَ لَهُمۡ أَنَّهُ ٱلۡحَقُّۗ – We will show them Our Signs in the universe, and in their own selves, until it becomes manifest to them that this (the Qur’an) is the truth]. [Surah Fussilat. Verse 53]
Indeed, when Allaah [The Exalted] informed us about His Oneness and that He alone is the One singled out in Perfection in every way, commanded us to worship Him alone without partners and that the religion should be devoted sincerely to Him alone, and stated that His speech, promise, threat, Messenger and book is truth, He then stated that He must show (humankind and Jinn) signs in themselves and in the universe of that which will make it clear that He is The Truth, and that everything else worshiped besides Him is false. The signs in the universe and the signs within themselves all confirm these mighty fundamentals by way of which it is known that Allah is The Truth, and that His Speech, His Book [i.e. the Qur’aan] and the Religion He has ordained are truth. https://salaficentre.files.wordpress.com/2022/06/49cf8-quranic_proofs_pdf_final.pdf