Is waswaas (devilish whisperings) necessarily always deen-related? I think that I am suffering from waswaas about cuss words. I think of cuss words all the time now, even regarding people whom I really care about like my parents and siblings and friends. I feel guilty because I am now saying them out loud due to frustration from having these thoughts. I say them out loud when I am alone, not with others. They are very bad, explicit, and perverted words. I do not know why I have such thoughts. I feel guilty, especially about the phrases about my parents, as I know that cussing your parents is the greatest sin ever on earth and that the Prophet cursed the one who does it. So, basically, I am a person of hell-fire. I am in despair, how can I repent? Also, like I asked earlier, is this waswaas? I also request that you supplicate for me that Allaah forgives this heinous act of mine. I love my parents, so please bear in mind that I did not say these disgusting words out of anger towards them, I only said them out of frustration towards the thoughts. My parents are not bad people, they always do good to me, and I appreciate them for it.

All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ʻalayhi wa sallam, is His slave and Messenger.

Waswaas is not always necessarily related to religious matters. One may experience waswaas about worldly affairs as well. However, waswaas might happen much more in religious matters because Satan is keen to ruin the person's religiosity and lead him to Hellfire. Allaah, The Exalted, says (what means): {Indeed, Satan is an enemy to you; so take him as an enemy. He only invites his party to be among the companions of the Blaze.} [Quran 35:6]

It seems that you are suffering from strong satanic whisperings. We advise you to strive in repelling and disregarding such whisperings and to seek refuge with Allaah whenever they occur to you. By doing so, they will not harm you, Allaah willing. Rather, they might be a good sign for you. Abu Hurayrah reported that a group of the Companions said to the Prophet, sallallaahu ʻalayhi wa sallam, "Verily we perceive in our minds that which every one of us considers it too grave to express." He, sallallaahu ʻalayhi wa sallam, said, "Do you really perceive it?" They said, "Yes." Upon this he, sallallaahu ʻalayhi wa sallam, remarked, "That is the faith manifest." [Muslim]

Moreover, Ibn ʻAbbaas narrated that a man came to the Prophet, sallallaahu ʻalayhi wa sallam, and said, "O Messenger of Allaah! One of us has thoughts of such nature that he would rather be reduced to charcoal than to speak about them." He, sallallaahu ʻalayhi wa sallam, said, "Allaah is the Most Great, Allaah is the Most Great, Allaah is the Most Great. Praise be to Allaah, Who has reduced the guile of the devil to evil prompting." [Abu Daawood]

You said that you feel guilty and abhor saying those words; so try to avoid willfully saying them because in such case you will be held accountable and bear a sin for it. However, if you feel that you are overpowered and you unwillingly say those words, then you will not be held accountable for that. Allaah, The Exalted, says (what means): {And there is no blame upon you for that in which you have erred but (only for) what your hearts intended. And ever is Allaah Forgiving and Merciful.} [Quran 33:5]

The Quran stated the supplications of the believers; Allaah, The Exalted, says (what means): {Our Lord, do not impose blame upon us if we have forgotten or erred.} [Quran 2:286] In relation to this verse, it has been narrated that Allaah would say, "I have done so." [Muslim]

We advise you to recite ruqyah (healing through Quranic recitation and supplication) and recite thikr (expressions of remembrance of Allaah) and supplications often, especially the reported thikr and supplications of the morning and evening. Please refer to fataawa 5531 and 24427.

Lastly, we would like to point out that the doctrine of true Muslims is that no specific individual is to be declared a  person of Paradise or Hellfire unless based on a text from the Quran or Sunnah because this belongs to the matters of the Unseen. The knowledge of the Unseen cannot be known except through divine revelation.

Allaah knows best.