Habitually telling lies when speaking is one of the characteristics of the hypocrites, as the Prophet (blessings and peace of Allah be upon him) said:
“There are four characteristics, whoever has them all is a pure hypocrite, and whoever has one of them has one of the characteristics of hypocrisy, until he gives it up:
1. when he is entrusted with something,
2. he betrays that trust, when he speaks he lies,
3. when he makes a covenant he betrays it,
4. and when he disputes he resorts to obscene speech.”
Narrated by al-Bukhaari (34) and Muslim (58).