Dear Hadi,
Dear Concerned about Guidance,
Of course, the best answer is that we do not know, and God knows best, but we believe that we are allowed to speculate, and so we will do that, based on the Quran.
In the Quran, it says that God guides whom He wills, and lets go astray (or even leads astray), whom He wills:
“And We never sent a messenger save with the language of his folk, that he might make (the message) clear for them. Then Allah sendeth whom He will astray, and guideth whom He will. He is the Mighty, the Wise” (Quran 14:4)
Therefore, we believe that, in the first and last analysis, guidance (or lack thereof) is something bestowed on individuals by God. It is, in fact, God’s decision.
This might make some people quite worried. Why would they worry? They would worry out of a fear that these decisions are either random, or capricious.
However, the Quran goes to great lengths in numerous verses (way, way too numerous to enumerate here) to show that neither is the case. The message which we see very clearly from the Quran is that, just as there are physical laws that govern the universe, there are also moral laws that govern the universe. The former operate in the physical realm, the latter operate in the spiritual realm. We will quote a very few verse snippets out of numerous verses in the Quran, which make the same points over and over.
Just as in the physical realm, where to every action, there is a reaction (one of Newton’s laws), we believe that in the spiritual realm, for every action there is a reaction.
Let us clarify, what we mean by looking again at the verse we just quoted, but by looking at the translation of Mohammed Asad:
“AND NEVER have We sent forth any apostle otherwise than with a message in his own people's tongue, so that he might make [the truth] clear unto them; but God lets go astray him that wills [to go astray], and guides him that wills [to be guided] -for He alone is almighty, truly wise” (Quran 14:4, Asad translation).
The Arabic, interestingly, admits both translations – that God guides whom He wills, or that God guides he who wills (to be guided). In this, we believe that there is a very strong statement of the moral law which governs the universe. We believe (and God knows best) that faith is a gift bestowed by God upon those who seek it. If one leans toward God, God will lean toward them, and bestow upon them faith.
This can be seen in the following verse snippet:
“Indeed, Allah leaves to stray whoever He wills, and guides to Himself whoever turns to Him” (Quran 13:27).
Conversely, God allows those to go astray who specifically choose that path - this is the reaction to their action in the moral scheme of the universe. Therefore, as we look at various verse snippets, we see that when God says that He will not guide someone, it is always because that person has specifically chosen misguidance:
“Through this test, He leaves many to stray, and guides many. And He leaves none to stray except the rebellious” (Quran 2:26).
“for God does not guide people who refuse to acknowledge the truth,” (Quran 2:264)
“Behold, God does not grace [such] evildoing folk with His guidance” (Quran 6:144)
The person’s action comes first, through an attitude of rebelliousness, or deliberate unbelief, or wicked behavior, and they squander their opportunity for guidance.
Therefore, the first point, to be succinct, is that when we say that God guides whom He wills and leaves go astray, whom He wills, those decisions are neither random nor capricious. They are governed by a moral law which the Quran makes very, very clear. It is then the human’s choice how to position himself vis a vis that law.
The second point is that when the gift of faith is bestowed, it is not a simple, fixed lump sum, such as giving someone a gift of $1 million and then that’s it -- there you have it. Rather, it is like getting the gift of a fresh sapling tree, which, if nurtured, sends strong roots into the ground, and grows into the sky, and bears beautiful fruit. Those who nurture the initial gift of faith will find their faith increased, and in that, they will find the serenity and peace that you asked about. We can see that in the following verses:
“[And now] We shall truly relate to thee their story: Behold, they were young men who had attained to faith in their Sustainer: and [so] We deepened their consciousness of the right way” (Quran 18:13)
“It is He who sent down tranquility into the hearts of the believers that they would add faith to their faith. To God belong the forces of the heavens and earth. God is All-Knowing and All-Wise” (Quran 48:4)
Thus, faith is not static. If cared for, it will increase, and hopefully lead to tranquility and inner peace.
Those, conversely, who take the gift of faith and deliberately squander it, they let that sapling die, and can then end up disbelieving in God, also, as you mentioned, and as the Quran mentions:
“How would God bestow His guidance upon people who have resolved to deny the truth after having attained to faith, and having borne witness that this Apostle is true, and [after] all evidence of the truth has come unto them? For, God does not guide such evildoing folk” (Quran 3:86)
In this verse, it is made clear that God will not guide those who deliberately squander the gift of faith after it has been given.
If they then change their attitude and repent, the door to God’s mercy is always open.
In peace.