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Sins of the Tongue in Islam
The tongue is one of many endowments Allâh bestowed upon His slaves. Although the tongue is a tiny organ, the person who uses it to comply with the orders of Allâh, the teachings of the Qur’ân, and the teachings of the Prophet may earn blessings in this world and the in Hereafter. However, the one who uses his tongue in disobedience to Allâh would not be displaying thankfulness to Allâh and would be heading towards his own destruction. Certainly, being thankful to Allâh means not to use the endowments bestowed by Allâh in what is forbidden. One needs to know the sins of the tongue could be small or enormous.
https://www.islam.ms/en/?p=62
Lying is forbidden in Islam
The Prophet Muḥammad, ṣallAllāhu `alayhi wa sallam, said: Which means: “Lying is not good, whether in seriousness or joking.” Related by al-Bayhaqiyy. and he said: which means: "Woe to him who talks to people and lies to make them laugh, woe to him, woe to him" related by imam 'Aḥmad in his Mousnad.
https://www.islam.ms/en/?p=126