Sahih Bukhari Volume 001, Book 002, Hadith Number 032.
Narated 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.)"