Why do adherents of other religions feel the same tranquility, serenity, and certainty of God answering their prayers as a Muslim does, even though Islam is the true religion?

The true believer possesses knowledge and certainty that enable him to repel doubts, whereas doubt indicates weakness of faith and the need to increase it. Exposing oneself to doubts with little knowledge is dangerous. Ibn al-Qayyim said about his Shaykh, Ibn Taymiyyah: "Do not make your heart like a sponge for objections and doubts, absorbing them. Instead, make it like a solid glass, through which doubts pass over its surface without settling within it."

It is not true that certainty and tranquility are the same for a Muslim and a non-Muslim, for one who believes in truth is not like one who believes in falsehood. Disbelievers follow conjectures and illusions, not certain knowledge.

As for the prayer of the distressed, it is answered regardless of one's religion. This is part of Allah's universal Lordship over His creation. Al-Qurtubi said: "Allah has guaranteed to answer the distressed when he supplicates Him... for sincerity has a position and a covenant with Him, whether found in a believer or a disbeliever, an obedient person or a transgressor." The answering of prayers is not limited to believers; Allah may answer the prayer of a disbeliever, and this does not indicate His satisfaction with him. Ibn Taymiyyah said: "All creation asks Allah, their believers and their disbelievers, and Allah may answer the prayers of disbelievers." Ibn al-Qayyim said: "Not everyone whose prayer Allah answers is someone He is pleased with, or loves, or is satisfied with his actions. For He answers the righteous and the wicked, the believer and the disbeliever."