Sahih Bukhari Volume 004, Book 053, Hadith Number 403.

Narated By 'Abdullah bin 'Amr : Allah's Apostle said, "Whoever has (the following) four characteristics will be a pure hypocrite: "If he speaks, he tells a lie; if he gives a promise, he breaks it, if he makes a covenant he proves treacherous; and if he quarrels, he behaves in a very imprudent evil insulting manner (unjust). And whoever has one of these characteristics, has one characteristic of a hypocrite, unless he gives it us."