I.
What befalls a Muslim of intrusive thoughts that make him doubt the existence of Allah, may He be Exalted, and prompt him to ridicule religious rituals and reject them is one of the trials that could be warded off by seeking the help of Allah, obeying Him and doing acts of worship, and offering a lot of supplication and remembering Allah a great deal (dhikr). The more the Muslim ignores these intrusive thoughts and pays no attention to them, the more that will help him to rid himself of those thoughts completely. Whatever happens of intrusive thoughts is part of the schemes and whispers of the Shaytan to divert the Muslim from obeying his Lord and make him follow the path of the misguided.
Let the one who is afflicted by this problem be reassured that he is not going to be held accountable for what occurs to him of doubts or denial of the truth, and he is not going to be held accountable for what he utters under the influence of those intrusive thoughts of oaths or divorce (talaq). Regarding that, please see the answer to question no. 12315.
II.
Tests and trials are something ordained by Allah and are necessary to test how strong a person’s faith is. Allah, may He be Exalted, says: {Do people think that they will be left alone because they say: We believe, and will not be tested?} [Aal-‘Ankabut 29:2]. One of the greatest reasons why Allah, may He be Exalted, tests people is so that as a result of this trial it will become clear who is sincere in his faith and who is not sincere. Allah, may He be Exalted, says: {But We have certainly tried those before them, and Allah will surely make evident those who are truthful, and He will surely make evident the liars} [Al-‘Ankabut 29:3].
Ibn al-Qayyim (may Allah have mercy on him) said: Allah’s wisdom dictated that people will inevitably be tried and tested so that through this test the good will become distinct from the evil; and it will become apparent who is fit to be a close friend of Allah and to be honoured by Him and who is not fit for that; and so as to purify the souls who are fit for that and cleanse them through the fire of that test as gold cannot be purified of its dross except through fire, because the human soul is by nature ignorant and prone to wrongdoing, and as a result of that ignorance and wrongdoing it accumulates evil or dirt that must be eliminated in the fire of that trial. If trials in this world are sufficient to eliminate this dirt, all well and good; otherwise he will be purified in the fire of hell, then after that, if he is purified and cleansed, he will be given permission to enter paradise.
End quote from Zad al-Ma`ad fi Hadi Khayr il-‘Ibad, 3/18.
The trial and test are not devoid of benefits for the believer who is patient and seeks reward with Allah. Either it will be a means of purifying him of sins, or it will be a means of raising him in status among those who are patient. In either case, it will benefit him if he is patient and seeks reward for that with which Allah, may He be Exalted, tests him.
For more information on the wisdom behind tests and trials, please see the answer to question no. 35914.
III.
What you attributed to the scholars, that the believer is only tested after he becomes steadfast and strong in faith, is not correct as far as we know; rather the correct view is the opposite: that the test comes first, and steadfastness and string faith come after that. Thus the test is what leads to steadfastness, which is what leads to good consequences in this world and the hereafter. Imam ash-Shafa`i (may Allah have mercy on him) was asked which is better for a man: to be made steadfast and string in faith or to be tested? He said: He cannot become steadfast unless he is tested, so steadfastness in this world can only come after being tested. Once he becomes steadfast, he will call others to Allah and strive to guide them. One of the texts which support what ash-Shafa`i (may Allah have mercy on him) said is the verse in which Allah, may He be Exalted, says: {And We made from among them leaders guiding by Our command when they were patient and [when] they were certain of Our signs} [As-Sajdah 32:24].
Ibn al-Qayyim (may Allah have mercy on him) said: Pain will inevitably come to every soul, whether it believes or does not believe, but the believer will go through pain and suffering in this world first, then he will have good consequences in this world and the hereafter, whereas the disbeliever will enjoy pleasure initially, then he will end up suffering everlasting pain.
– then he quoted the words of Imam ash-Shafa`i –
Then he said:
Allah, may He be Exalted, tested the Messengers of strong will, then when they showed patience, He granted them power and steadfastness. So no one should think that he will be saved from pain at all; rather people of wisdom are those who prefer to be spared great and ongoing pain [in the hereafter] in return for a little, temporary pain [in this world]. The most wretched of people are those who prefer to avoid a little, temporary pain in return for great and ongoing pain.
End quote from Zad al-Ma`ad, 3/14, 15.
IV.
Supplication (du`a’) is one of the greatest means of warding off and alleviating calamities. Allah, may He be Glorified and Exalted, says:
{And We have already sent [messengers] to nations before you, [O Muḥammad]; then We seized them with poverty and hardship that perhaps they might humble themselves [to Us].
Then why, when Our punishment came to them, did they not humble themselves? But their hearts became hardened, and Shaytan made attractive to them that which they were doing} [Al-An`am 6:42-43]
And:
{And We had gripped them with suffering [as a warning], but they did not yield to their Lord, nor did they humbly supplicate, [and will continue thus]} [Al-Mu’minun 23:76].
Ibn al-Qayyim (may Allah have mercy on him) said: Supplication is one of the most efficacious remedies, for it is the antidote to calamity; it engages with it and fights it, and prevents it from gaining a foothold, and it relieves it and reduces it if it has taken hold. And it is the weapon of the believer.
End quote from Al-Jawab al-Kafi, p. 4.
The people of Yunus benefited greatly from supplication when they saw the punishment coming, and that was the cause of their being saved from it, and that happened after they had believed.
Ibn Kathir (may Allah have mercy on him) said: There was no city among the cities of the past where all of its people believed in its prophet except the people of Yunus, who are the people of Nineveh. The cause of their belief was nothing other than fear that the punishment the messenger had warned them about would befall them, after they saw it approaching with their own eyes, after the messenger had left them. At that point they turned to Allah, seeking His help, beseeching Him and showing humility; they brought their children, their mounts and their livestock and asked Allah, may He be Exalted, to ward off from them the punishment that their prophet had warned them about. Then Allah had mercy on them; He removed the punishment from them and gave them respite, as He, may He be Exalted, says:
{There was no city that believed [after seeing the punishment] and benefitted from its faith except the people of Yoonus. When they believed, We removed from them the punishment of disgrace in this world, and allowed them to enjoy life for a while} [Yunus 10:98].
End quote from Tafsir Ibn Kathir, 4/297.
There are some things which, if the one who is stricken by calamity reflects on them, he will realise that his calamity is mild. See the answer to question no. 71236.
How can the afflicted person find out whether the calamity he is facing is by way of punishment or a trial to raise him in status? See the answer to question no. 112905.
We ask Allah to grant you relief from what you are suffering and increase you in faith, certainty and guidance.
And Allah knows best.