Cursing, lying, backbiting, gossiping, vain, idle talk, slander are all haram/forbidden and not allowed and is sinful and even your tongue can get you into hell too so read this so you will commit less sins
One of the hallmarks of righteous behavior is good speech. A person who stays mindful of Allah (God) will want to refrain from sins of the tongue such as backbiting, slander, gossip, lying, swearing, cursing and vain talk. The Qur'an and Hadith (the narrated traditions of the Prophet Muhammad, peace be upon him*) warn against these sins of the tongue.
Guarding one's speech is so important that Muslims will be held accountable for everything they say: “Not a word does he (or she) utter but there is a watcher by him ready (to record it)” (Qur'an 50:18).
Lying in Islam
Lying is a sin in Islam, and considered an evil act which can lead to the hellfire. Exaggerating, deception and fabricating co-called "white lies" are also sinful, even if used purely in jest or to pacify a child.
Under special circumstances, Islam gives exception to telling lies. The Messenger of Allah (peace and blessings of Allah be upon him) said: “Lies are not appropriate except in three cases: when a man speaks to his wife to please her, telling lies at times of war, and lying in order to bring about reconciliation between people.” (Reported Hasan by Shaykh al-Albaani)
Gossip, Backbiting and Slander in Islam
Gossip involves the act of talking about others, and often involves backbiting or slander. Both are grave sins in Islam. A well-known hadith distinguishes backbiting from slander in the following way:
The Prophet Muhammad (peace be upon him) said, "Do you know what backbiting is?" They said, "Allah and His Messenger know best." He then said, "It is to say something about your brother that he would dislike." Someone asked him, "But what if what I say is true?" The Messenger of Allah said, "If what you say about him is true, you are backbiting him, but if it is not true then you have slandered him." (Muslim)
Allah cautions against backbiting in the Qur'an: "O you who believe! Avoid much suspicion, in deeds some suspicions are sins. And spy not neither backbite one another. Would one of you like to eat the flesh of his dead brother? You would hate it (so hate backbiting). And fear Allah, verily, Allah is the one who accepts repentance, Most Merciful." (49: 12)
Cursing and Swearing in Islam
Invoking Allah to curse someone or while making an oath is a serious matter. It becomes sinful if a Muslim does so carelessly, without sincerity or doesn't honor what was promised.
It is also sinful for to curse another Muslim or to swear by someone or something other than Allah.
Think Before Speaking to Avoid Vain Speech or Idle Talk
Religious scholars advise Muslims to think before speaking.
If a Muslim feels at all uncertain, he should keep quiet rather than risk saying something which contradicts Islamic belief or behavior. This doesn't mean that a person can't engage in casual conversation, but rather that he should guard his speech and choose his words carefully.
Good Speech Can Lead to Paradise – Sins of the Tongue Can Lead to Hell
The ultimate goal for a Muslim is to be admitted to Paradise. Good speech plays a role in earning that reward: "The believers are successful, whose who in their prayer have khushu (fear of Allah) and those who refrain from vain talk..." (Qur'an 23:1-3)
Conversely, sins of the tongue can lead a Muslim to hell. The Prophet Muhammad (peace be upon him) said: "A man may be so close to Paradise such that the distance between him and it is one derah (an arm's length) and he speaks a word and he becomes distant from it further than Sana." (Ahmed)
He (peace be upon him) is also quoted as saying: "People are not thrown into the hellfire on their faces or noses except due to the result of their tongues.” (Ahmad and al-Tirmidhi )
It is essential, then, that Muslims refrain from sins such as gossip, backbiting, slander, lying and cursing. By remembering and fearing Allah, a Muslim will find it easier to choose his words carefully and consider whether he's saying something beneficial or harmful to himself
http://suite101.com/article/sins-of-the-tongue-a165207
So watch what you say and be polite and speak politely since you are rewarding for only good deeds and righteousness and you sin for wrongdoings and evilness
One of the hallmarks of righteous behavior is good speech. A person who stays mindful of Allah (God) will want to refrain from sins of the tongue such as backbiting, slander, gossip, lying, swearing, cursing and vain talk. The Qur'an and Hadith (the narrated traditions of the Prophet Muhammad, peace be upon him*) warn against these sins of the tongue.
Guarding one's speech is so important that Muslims will be held accountable for everything they say: “Not a word does he (or she) utter but there is a watcher by him ready (to record it)” (Qur'an 50:18).
Lying in Islam
Lying is a sin in Islam, and considered an evil act which can lead to the hellfire. Exaggerating, deception and fabricating co-called "white lies" are also sinful, even if used purely in jest or to pacify a child.
Under special circumstances, Islam gives exception to telling lies. The Messenger of Allah (peace and blessings of Allah be upon him) said: “Lies are not appropriate except in three cases: when a man speaks to his wife to please her, telling lies at times of war, and lying in order to bring about reconciliation between people.” (Reported Hasan by Shaykh al-Albaani)
Gossip, Backbiting and Slander in Islam
Gossip involves the act of talking about others, and often involves backbiting or slander. Both are grave sins in Islam. A well-known hadith distinguishes backbiting from slander in the following way:
The Prophet Muhammad (peace be upon him) said, "Do you know what backbiting is?" They said, "Allah and His Messenger know best." He then said, "It is to say something about your brother that he would dislike." Someone asked him, "But what if what I say is true?" The Messenger of Allah said, "If what you say about him is true, you are backbiting him, but if it is not true then you have slandered him." (Muslim)
Allah cautions against backbiting in the Qur'an: "O you who believe! Avoid much suspicion, in deeds some suspicions are sins. And spy not neither backbite one another. Would one of you like to eat the flesh of his dead brother? You would hate it (so hate backbiting). And fear Allah, verily, Allah is the one who accepts repentance, Most Merciful." (49: 12)
Cursing and Swearing in Islam
Invoking Allah to curse someone or while making an oath is a serious matter. It becomes sinful if a Muslim does so carelessly, without sincerity or doesn't honor what was promised.
It is also sinful for to curse another Muslim or to swear by someone or something other than Allah.
Think Before Speaking to Avoid Vain Speech or Idle Talk
Religious scholars advise Muslims to think before speaking.
If a Muslim feels at all uncertain, he should keep quiet rather than risk saying something which contradicts Islamic belief or behavior. This doesn't mean that a person can't engage in casual conversation, but rather that he should guard his speech and choose his words carefully.
Good Speech Can Lead to Paradise – Sins of the Tongue Can Lead to Hell
The ultimate goal for a Muslim is to be admitted to Paradise. Good speech plays a role in earning that reward: "The believers are successful, whose who in their prayer have khushu (fear of Allah) and those who refrain from vain talk..." (Qur'an 23:1-3)
Conversely, sins of the tongue can lead a Muslim to hell. The Prophet Muhammad (peace be upon him) said: "A man may be so close to Paradise such that the distance between him and it is one derah (an arm's length) and he speaks a word and he becomes distant from it further than Sana." (Ahmed)
He (peace be upon him) is also quoted as saying: "People are not thrown into the hellfire on their faces or noses except due to the result of their tongues.” (Ahmad and al-Tirmidhi )
It is essential, then, that Muslims refrain from sins such as gossip, backbiting, slander, lying and cursing. By remembering and fearing Allah, a Muslim will find it easier to choose his words carefully and consider whether he's saying something beneficial or harmful to himself
http://suite101.com/article/sins-of-the-tongue-a165207
So watch what you say and be polite and speak politely since you are rewarding for only good deeds and righteousness and you sin for wrongdoings and evilness