“This (Quran) is enlightenment for mankind and guidance and mercy for a people who have Faith with certainty.
What! Do those who commit evils think that We shall hold them equal with those who believe and do righteous deeds -
that equal will be their life and their death?
Ill is the judgment that they make.
And Allah created the heavens and earth with truth and so that every soul may be rewarded for what it has earned, and they will not be wronged.” (Surah Al Jathiya, 45: 21-23)
In the first verse (verse 21), Allah says that the Quran and the words of the Quran contain clear proofs/signs for humanity. If someone carefully studies it with Taqwa (fear of Allah, with piety), and in any aspect that he cares to study it, then, he shall therein certainly will find very clear evidence. Then Allah says it is a guidance and a mercy for the believers, for those who have faith (Iman), and who have a certainty in this book (and its words).
In another verse (verse 22), Allah says: “Do those who commit evils think that We shall hold them equal with those who believe and do righteous deeds - that equal will be their life and their death.” In other words, do those who do evil deeds think that We will give them the same treatment so that their lives and deaths become similar to the lives and deaths of the believers? No it’s impossible. For those who have faith (who are believers) and do righteous deeds, Allah will make them on this earth itself such treatment that will distinguish them from all others. And it is indeed such a treatment that shall be ongoing.
So, the treatment which Allah reserves for the true believers is quite different from the treatment which the people who are immersed in evil shall receive. This treatment is different and it is distinguished and when you analyze this treatment closely then you will know for sure that those who are indeed recipient of this treatment are indeed the servants of Allah and that the others are from Iblis.