Allah's Messenger (ﷺ) said, "The signs of a hypocrite are three: Whenever he speaks, he tells a lie; and whenever he promises, he breaks his promise; and whenever he is entrusted, he betrays (proves to be dishonest)".
Sahih al-Bukhari Book 78, Hadith 122
← Previous Hadith The Prophet (ﷺ) said, "Truthfulness leads to righteousness, and righteousness leads to Paradise. And a man keeps on telling the truth until he becomes a truthful person. Falsehood leads to Al-Fajur (i.e. wickedness, evil-doing), and Al-Fajur (wickedness) leads to the (Hell) Fire, and a man may keep on telling lies till he is written before Allah, a liar."

Sahih al-Bukhari Book 78, Hadith 121 Next Hadith → The Prophet (ﷺ) said, "I saw (in a dream), two men came to me." Then the Prophet (ﷺ) narrated the story (saying), "They said, 'The person, the one whose cheek you saw being torn away (from the mouth to the ear) was a liar and used to tell lies and the people would report those lies on his authority till they spread all over the world. So he will be punished like that till the Day of Resurrection."'

Sahih al-Bukhari Book 78, Hadith 123