Allaah says (interpretation of the meaning): “. . . So shun the abomination (worship) of idols, and shun lying speech (false statements) - hunafaa’ Lillah (i.e., to worship none but Allaah), not associating partners (in worship, etc.) unto Him . . .” [al-Hajj 22:30-31]
‘Abd al-Rahmaan ibn Abi Bakrah (may Allaah be pleased with him and his father) reported that his father said: “We were with the Messenger of Allaah (peace and blessings of Allaah be upon him) when he said: ‘I fear for you three major sins’ - three times: ‘associating partners with Allaah, disobedience to parents, and -’ - he was reclining but he sat up at this point and said: ‘ - and bearing false witness.’ He kept repeating this with such fervour that we wished he would stop (for his own sake).” (Reported by al-Bukhaari, see al-Fath, 5/261).
The warning against bearing false witness was uttered repeatedly because people take it too lightly and there are many motives for doing so, such as hatred and envy. The resulting corruption is great indeed: how many people have lost their rights because of false witness! How many innocent people have been treated unjustly, and how many people have gained what they did not deserve, because of it!
An example of the ways in which people take this matter lightly is what sometimes happens in the courts, when a person might say to someone he has only just met, "Testify for me and I will testify for you." So one might testify for the other in a case where he does not have the necessary knowledge of what really happened, like testifying that this person owns a piece of land or a house, or recommending him when he has never seen him before that day in court. This is lying and false witness, whereas testimony should be as described in the Book of Allaah: ". . . we testify not except according to what we know . . ." [Yoosuf 12:81]
Listening to music and musical instruments
Ibn Mas’ood (may Allaah be pleased with him) used to swear by Allaah that the aayah “And of mankind is he who purchases idle talk to mislead (men) from the Path of Allaah . . .” [Luqmaan 31:6] referred to singing. Abu ‘Aamir and Abu Maalik al-Ash’ari (may Allaah be pleased with them) reported that the Prophet (peace and blessings of Allaah be upon him) said: “Among my ummah will be those who make permissible al-hira(adultry or zinah), silk, khamr and musical instruments . . .” (Reported by al-Bukhaari; see al-Fath, 10/51).Anas (may Allaah be pleased with him) reported that the Prophet (peace and blessings of Allaah be upon him) said: “In this ummah there will be punishments of earthquakes, showers of stones and deformity (transformation into animals); that will be when the people drink khamr, listen to female singers and play musical instruments.” (See al-Silsilah al-Saheehah, 2203; attributed to Ibn Abi’l-Dunyaa, Dhamm al-Malaahi; the hadeeth was narrated by al-Tirmidhi, no. 2212).
The Prophet (peace and blessings of Allaah be upon him) forbade the “koobah” (a kind of drum), and described the flute as the voice of the immoral fool. The early scholars such as Imaam Ahmad, may Allaah have mercy on him, stated that musical instruments such as the 'ood (lute), tanboor (a long-necked stringed instrument), reed flute, rabaab (stringed instrument resembling a fiddle) and cymbal, were haraam; no doubt modern instruments such as the violin, qaanoon (stringed musical instrument resembling a zither), organ, piano, guitar, etc., are also included in the Prophet’s prohibition on musical instruments, because their effect and impact is greater than that of the ancient instruments mentioned in some ahaadeeth. They are even more intoxicating than khamr, as scholars such as Ibn al-Qayyim mentioned. No doubt the prohibition, and the sin involved, are greater when the music is accompanied by singing and the voices of female singers, and it is even worse when the lyrics speak of love and describe physical beauty. Hence the scholars said that singing paves the way for zinaa (adultery or fornication), and that it makes hypocrisy grow in the heart. Generally speaking, music and singing form one of the greatest temptations of our times.
What is very difficult is the fact that nowadays music is a part of so many things, such as clocks, doorbells, children’s toys, computers, telephones, etc., and avoiding it takes a great deal of determination. Allaah is the source of help.
Many gatherings produce nothing but gossip about other Muslims and slander of their honour. This is something which Allaah has forbidden His slaves, and has drawn the most repulsive analogy to put them off. He says (interpretation of the meaning): “. . . neither backbite one another. Would one of you like to eat the flesh of his dead brother? You would hate it . . .” [al-Hujuraat 49:12]
The Prophet (peace and blessings of Allaah be upon him) explained the meaning of this aayah. He said: “Do you know what gheebah (gossip or backbiting) is?” They said, “Allaah and His Messenger know best.” He said: "To say something about your brother that he does not want to be said." He was asked, "What do you think if what is said about him is true?" He said, "If what you say about him is true, this is backbiting, and if what you say about him is not true, this is a lie." (Reported by Muslim, 4/2001).
Gossip or backbiting means saying something about a Muslim which may be true but which he does not like to hear spoken, whether it be about his physical appearance, his adherence to religion, his worldly affairs, his self, his behaviour or his character. There are many forms of gossip, including talking about a person's faults and imitating him to make fun of him.
People take the matter of gheebah very lightly, although it is very serious in the sight of Allaah, as is indicated by the words of the Prophet (peace and blessings of Allaah be upon him): "There are seventy-two forms of riba, the least of which is as bad as a man having intercourse with his own mother, and the worst of which is when a man slanders the honour of his brother." (Silsilah al-Saheeh, 1871).
Whoever is present in a gathering where gossip
takes place should "forbid what is evil" and defend his
absent brother. The Prophet 
(peace and
blessings of Allaah be upon him) encouraged us to do this when he
said: "Whoever defends the honour of his Muslim brother, Allaah
will protect his face from the Fire on the Day of Resurrection."
(Reported by Ahmad, 6/450; see also Saheeh
al-Jaami', 6238).
Some people go about repeating the words of others to cause trouble between people; this is one of the greatest causes of broken relations and stirring up feelings of hatred among people. Allaah condemned the one who does this (interpretation of the meaning): "And obey not everyone who swears much, - and is considered worthless, a slanderer, going about with calumnies." [al-Qalam 68:10-11]
Hudhayfah reported that the Prophet (peace and blessings of Allaah be upon him) said: "No eavesdropper will enter Paradise." (Reported by al-Bukhaari, see al-Fath, 10/472; "eavesdropper" here refers to a person who eavesdrops on others without their knowing, then goes and tells others what he has heard)
Ibn 'Abbaas said: "The Prophet (peace and blessings of Allaah be upon him) passed by one of the gardens of Madeenah, and heard the sound of two people being punished in their graves. The Prophet (peace and blessings of Allaah be upon him) said: "They are being punished, but they are not being punished for any major sin; one of them used never to clean himself properly after urinating, and the other used to spread malicious slander . . ." (Reported by al-Bukhaari; see Fath al-Baari, 1/317).
One of the worst forms of this sin is to cause trouble between a husband and wife, or vice versa, or to tell one's boss what other employees are saying, in order to create trouble. All of this is haraam.
Looking into people's houses without their permission
Allaah says (interpretation of the meaning):
"O you who believe! Enter not houses other than your own, until you have asked permission and greeted those in them . . ." [al-Noor 24:27]
The Prophet (peace and blessings of Allaah be upon him) explained that the reason why permission was to be sought was for fear that the person seeking to enter might see something private in the house: "The rule of seeking permission has been established for the sake of (not) seeing." (Reported by al-Bukhaari, see Fath al-Baari, 11/24). Nowadays, when houses and buildings are too close to one another or even attached, and doors and windows face one another, the possibility of neighbours seeing one another has increased greatly. Many people do not lower their gaze, and some of those who live on higher floors may deliberately look down from their roofs and windows into neighbouring homes that are lower than their own. This is an act of betrayal and an invasion of their neighbours' privacy, as well as being the way that leads to haraam deeds. A great deal of misery and trouble has resulted from this, and that fact that the Sharee'ah counts the eye of the one who spies as worthless is sufficient proof of the seriousness of the matter. The Messenger of Allaah (peace and blessings of Allaah be upon him) said: "Whoever looks into somebody's house without their permission, it is permissible for them to put out his eye." (Reported by Muslim, 3/1699). According to another report, he said: "Put out his eye, and there will be no penalty or retribution." (Reported by Imaam Ahmad, 2/385; see also Saheeh al-Jaami', 6022).
Two people conversing privately to the exclusion of a third
This is one of the problems that exist in social gatherings, and it is one of the ways in which Shaytaan divides the Muslims and makes some of them hate others. The Prophet (peace and blessings of Allaah be upon him) explained the rule and the wisdom behind it: "If you are three, then two should not converse privately to the exclusion of a third until you are joined by other people, because this will make him sad." (Reported by al-Bukhaari, see Fath al-Baari, 11/83). This also includes three people talking privately to the exclusion of a fourth, and so on, and two people speaking in a language which the third does not understand, because this is undoubtedly a form of disdain towards the third, and gives the impression that they intend to hurt him, etc.
Some people deliberately fabricate dreams and visions that they have not really seen, as a means of gaining spiritual prestige and fame, or for some material gains, or to scare their enemies, and the like. Many of the common people have a strong beliefs in dreams and are easily deceived by such lies. The Prophet (peace and blessings of Allaah be upon him) issued a stern warning to whoever does such a thing: "One of the worst types of lie is for a man to claim to belong to someone other than his real father, or to claim to have seen something which he did not see, or to attribute to the Messenger of Allaah (peace and blessings of Allaah be upon him) words that he did not say." (Reported by al-Bukhaari, see al-Fath, 6/540).The Prophet (peace and blessings of Allaah be upon him) also said: "Whoever claims to have seen a dream which he did not see will be ordered to tie two grains together, and he will never be able to do it . . ." (Reported by al-Bukhaari; see al-Fath, 12/427). Tying two grains together is impossible, so the punishment will fit the crime.