Sahih Bukhari | Volume 1 | Hadith Number 32

Narrated by Abu Huraira
The Prophet said, "The signs of a hypocrite are three:

1. Whenever he speaks, he tells a lie.

2. Whenever he promises, he always breaks it (his promise).

3. If you trust him, he proves to be dishonest. (If you keep something as a trust with him, he will not return it.)"