To attribute any statement towards someone which was not his/her or them, is lying. Conversion of active voice into passive voice or changing from direct conversation into indirect conversation is not considered as lying as long as the meanings are not changed. If the meaning is changed then it will not remain the purpose of original statement. So it will be taken as lying. Not only in Islam but also nearly all religions consider it bad.
Holy Prophet may Allah bless him and his holy progeny with peace said, O people ! Beware that I am telling you about big sins. Sharing with Allah, Disobeying the parents and lying. At another place it is narrated that if all the evils are locked in a room, lying is the only key. It means that lying opens the door to evils. When a Muslim is lying , seventy thousand angels curse him. A strong unpleasant stink appears from his heart and soul which spreads till Arsh.
No doubt there is no any other sin as compared to lying. Some lies are the cause of quarrels among people. Similarly due to some lies, fighting can takes place among tribes. Due to such lies, uncounted lives get ruined. A judge or jury declares the judgement on the basis of evidences. False evidences may lead to false judgement. An innocent can be considered as Criminal. If someone lies in the name of Islam, Koran Karim, Holy Prophet or in the name of Allah. His sin is unforgivable. Now a days we listen about Islamic militants groups in different countries. Their leaders lied in the name of Allah. They misguided people and the result is in front of us. All the Muslim Ummah is suffering .
Due to lying of one person , a lot of people suffer physically , mentally and economically. As much as the people suffer the sin will be bigger. Complete abstaining from all types of lies is compulsory as per quran for kids you are first school if u tell a lie in front of them they will learn from you. There is no Optimization in telling lies, either in serious issue or in jokes. Even you should not make promise with your kids if you do not intend to do so.
Allah says in Surat Nahal that only those people tell a lie who do not believe in signs of Allah. In Surat Zumr Allah says that Truly Allah does not provide guidance to liar and Ungrateful persons. It is clear from the ayahs of Koran Karim and sayings of Holy Prophet may Allah bless him and his holy progeny with peace. A Muslim must avoid telling lies ever and ever. Parents are responsible for their kids proper teaching and training. We have arranged online teaching of quran for kids . We teach basic Islamic knowledge to make your kids good Muslim.