The prohibition of lying:

　　Allah The Almighty Says (what means): {“They only invent falsehood who do not believe in the verses of Allah, and it is those who are the liars.”} [Quran 16:105] Commenting on this verse, Ibn Katheer said, “Allah The Almighty informs us that His Messenger is not a liar, because lying is only the practice of the most evil people from amongst the disbelievers and polytheists who do not believe in the verses of Allah The Almighty. It is such people who are known among people to be liars, while Muhammad was the most truthful person amongst his people and the kindest to others and the most wise. He was so truthful that his people gave him the nickname of ('The Truthful' and 'The Trustworthy'). This is why Hercules – the Roman king - asked Abu Sufyan about this very quality saying, ‘Was he ever known to be a liar before claiming prophethood?’ to which Abu Sufyan replied: 'No'. Thereupon Hercules said, ‘Then he would not give up lying to people and start lying on God.’”

　　Abu Hurayrah narrated that the Prophet, said: “The signs of a hypocrite are three; he lies when talking, he breaks his promises and he deceives when entrusted […] anyone who possesses all such qualities is a pure hypocrite” [Al-Bukhari, Muslim].

　　Imam An-Nawawi commented on this narration saying, “The sound opinion about the interpretation of this narration is that these are the qualities of hypocrites, and the one who possesses them resembles hypocrites […] his, saying: “… anyone who possesses all such qualities is a pure hypocrite…” means that the person very closely resembles the hypocrites. Some scholars said that this applies to the person whose character is as such most the time, but the one who rarely does so is not included in the description. Imam At-Tirmithi reported that the narration refers to practical hypocrisy according to the scholars.”

　　The evil consequence of lying:

　　A liar is warned that he is liable to be punished in both this life and the Hereafter with humiliating and destructive punishments such as:

　　· Rejecting testimony: Ibn Al-Qayyim said, “Lying is one of the strongest reasons to reject the testimony and narration of a person, because the tool itself is corrupted (tongue). This is similar to the testimony of a blind person regarding sighting the crescent of Ramadan, and the deaf for something that he heard. A lying tongue is an organ that has become defective and stopped functioning. In fact it is even worse, because the worst thing a person can possess is a lying tongue”

　　Tearing of the face in the Hereafter: Samurah ibn Jundub said, “The Messenger of Allah very often used to ask his Companions, : "Has any one of you seen a strange dream?" So dreams would be narrated to him by those whom Allah The Almighty willed to relate. One day he said: "Last night I had a vision in which two men (angels) came to me and woke me up and said to me, `Proceed!' I set out with them and we came across a man lying down, and behold, another man was standing over his head, holding a big rock. Behold, he was throwing the rock at the man's head, smashing it. When he struck him, the stone rolled away and he went after it to get it, and no sooner had he returned to this man, his head was healed and restored to its former condition. The thrower (of the rock) then did the same as he had done before.

　　I said to my two companions, `Subhanallah (Glory be to Allah)! Who are these?' They said: `Proceed, proceed.' So we proceeded and came to a man lying in a prone position and another man standing over his head with an iron hook, and behold, he would put the hook in one side of the man's mouth and tear off that side of his face to the back (of the neck), and similarly tear his nose from front to back, and his eyes from front to back. Then he turned to the other side of the man's face and did just as he has done with the first side. He had hardly completed that (second) side when the first returned to its normal state.”

　　Then when he informed the Companions about the explanation of what he had seen, he said: “I said to them, `I have seen many wonders tonight. What does all that mean which I have seen?' They replied, `We will inform you: […] As for the man you came upon, whose sides of mouth, nostrils and eyes were torn off from front to back, he is the symbol of the man who goes out of his house in the morning and tells lies that are spread all over the world …” [Al-Bukhari].