hadith

Prophet (peace be upon him) said:
"The signs of a hypocrite are three:
Whenever he speaks, he tells a lie.
Whenever he promises, he always breaks it (his promise).
If you trust him, he proves to be dishonest. (If you keep something as a trust with him, he will not return it.)"

Narrated Abu Huraira Sahih Hadith Volume 1 : 32