The Source of the Judgement is Quran, the Guide...
And verily, this (the Quran) is indeed a Reminder for you and your people, and you will be questioned (about it).
We have seen that the content and framework of religion is determined by the Quran, which contains God's commands, and that seeking a source of command outside of this is delusion, and accepting it is polytheism. Let us then examine the characteristics of the Quran, about which our Lord says we will be questioned in the future.
Indeed in their stories, there is a lesson for men of understanding. It (the Quran) is not a forged statement but a confirmation of the Allah's existing Books [the Taurat (Torah), the Injeel (Gospel) and other Scriptures of Allah] and a detailed explanation of everything and a guide and a Mercy for the people who believe.
The Quran mentions the guiding nature of the following verses . The Quran itself explains this concept as follows:
Alif-Lam-Ra. [These letters are one of the miracles of the Quran, and none but Allah (Alone) knows their meanings]. (This is) a Book which We have revealed unto you in order that you might lead mankind out of darkness (of disbelief and polytheism) into light (of belief in the Oneness of Allah and Islamic Monotheism) by their Lord's Leave(permission) to the Path of the All-Mighty, the Owner of all Praise.
It has been repeated that the Quran is a guide for believers, those who behave well, those who are pious (sensitive), and those who believe.
And truly, it (this Quran) is a guide and a mercy to the believers.
A guide and a mercy for the Muhsinun (good-doers).
This (Quran) is a guidance. And those who disbelieve in the Ayat (proofs, evidences, verses, lessons, signs, revelations, etc.) of their Lord, for them there is a painful torment of Rijz (a severe kind of punishment).
This (the Quran) is a plain statement for mankind, a guidance and instruction to those who are Al-Muttaqun.
(Godwary-righteous persons who abstain from all kinds of sins and evil deeds which He has forbidden and love Allah much perform all kinds of good deeds which He has ordained)
This (Quran) is a clear insight and evidence for mankind, and a guidance and a mercy for people who have Faith with certainty.
When you do not bring them a sign(evidence), they say, ‘Why do you not improvise one?’ Say, ‘I only follow what is revealed to me from my Lord; these are insights from your Lord, and a guidance and mercy for a people who have faith.’
Allah has sent down the best of discourses, a scripture [composed] of similar motifs, whereat shiver the skins of those who fear their Lord, then their skins and hearts relax at Allah’s remembrance. That is Allah’s guidance, by which He guides whomever He wishes; and whomever Allah leads astray, has no guide.
Had We made it a non-Arabic Quran, they would have said, ‘Why have not its signs been articulated?’ ‘What! A non-Arabian [scripture] and an Arabian [prophet]!?’ Say, ‘It is guidance and healing for those who have faith. As for those who are faithless, there is a deafness in their ears and it is lost to their sight: [to them it is as if] they were called from a distant place.’
This is the Book, there is no doubt in it, a guidance to the Godwary.(Muttaqun - explained above verse 3:138)
Certainly We have brought them a Book, which We have elaborated with knowledge, as a guidance and mercy for a people who have faith.
Say, ‘It has been revealed to me that a team of the jinn listened [to the Quran] and they said, “Indeed we heard a wonderful Quran, which guides to rectitude. Hence, we have believed in it and we will never ascribe any partner to our Lord.
We did not send down the Book to you except [for the purpose] that you may clarify for them what they differ about, and as a guidance and mercy for a people who have faith.