Narrated 'Abdullah bin 'Amr: The Prophet said, "Whoever has the following four (characteristics) will be a pure hypocrite and whoever has one of the following four characteristics will have one characteristic of hypocrisy unless and until he gives it up. 1. Whenever he is entrusted, he betrays. 2. Whenever he speaks, he tells a lie. 3. Whenever he makes a covenant, he proves treacherous. 4. Whenever he quarrels, he behaves in a very imprudent, evil and insulting manner."
[Hadith from Sahih Bukhari, Book No. 2: Belief, Hadith No. 33]