In The Name of Allaah, The Most Merciful The Bestower of Mercy
Imaam Sadi (rahimahullaah) said:
Besides that group of haughty and confused (atheists), it has been established regarding all the nations that they testified to the (truthfulness) of that which the Messengers were upon of exalted manners, lofty characteristics and the true creed they came with, through which Allaah gave success to the Religious and worldly affairs; (and through which) He (The Most High) guided the slaves to every goodness, every act of righteousness and success, in general and specific, and in this life and the next.
He (The Most High) supported them (i.e. the Messengers) with clear signs and evidences that have been in continuous succession and occurrence, (in a manner) not equal to anything amongst those affairs that take place continuously. (These continuous and successive clear signs and evidences of the Messengers) have been transmitted by the nations and generations, and they are foremost in rank amongst those (events) of reality and at the highest level of credibility. And in particular, the (last) Prophet and leader of (the people) Muhammad (sallal-laahu-alayhi-wasallam), indeed the creation testified to the truthfulness of that which he came with. They acknowledged it, and his allies and enemies submitted to it.
And had it not been for anything else except this Qur’aan he came with, and by way of which Allaah challenged Jinn and Mankind to either bring forth something similar to it or ten verses, or one surah, due to its great literary composition, it’s beautiful and lofty literary style, and its rulings being the most perfect and excellent of rulings, and its news of the past and future affairs of the unseen, which are related to the affairs of the creation and the (affairs) of the Creator (Allaah); therefore, the one who is acquainted with something of the state of affairs of the Messengers, their truthfulness, the reports (transmitted) about them and the rulings (they came with), he will acknowledge that those who reject that which the Messengers came with have displayed arrogance in the presence of those affairs that are clearly perceived. They have belied clear discernment and obstinately turned away from the sound sources of knowledge, and they have rejected the affairs that are known with certainty.
And without doubt, they are either obstinate opponents of the truth or blind followers of the obstinate opponents. They are just like what Allaah has stated about their leaders: ‘’And they belied them (those Ayat) wrongfully and arrogantly, though their ownselves were convinced thereof [i.e. those (Ayat) are from Allah, and Musa (Moses) is the Messenger of Allah in truth, but they disliked to obey Musa (Moses), and hated to believe in his Message of Monotheism]. So see what was the end of the Mufsidun (disbelievers, disobedient to Allah, evil-doers, liars.).’’ [Soorah An-Naml: Ayah: 14]
If they do not believe, and if they do not testify to the truthfulness of that which the Messengers came with, ‘’ Then in which speech after Allah and His Ayat will they believe?’’ [Soorah Al-Jaathiyah: Ayah: 6]
As for the men of understanding, indeed Allaah (The Most High) stated about them (that they said): “Our Lord! Verily, we have heard the call of one (Muhammad) calling to Faith: ‘Believe in your Lord,’ and we have believed.’’ [Soorah Aal Imraan: Ayah: 193] ‘’Our Lord! We believe in what You have sent down, and we follow the Messenger ['Iesa (Jesus)]; so write us down among those who bear witness (to the truth i.e. La ilaha ill-Allah – none has the right to be worshipped but Allah).[Soorah Aal Imraan: Ayah:53]
Source: Al-Adillatul Qawaatiq Wal-Baraaheen Fee Ibtaalil Usoolil Mulhideen: page: 29-30]
Translated by: Abu Mu-aawiyyah (Abdullaah Al-Gambi)