Prophet Muhammad (peace be upon him) said
"There are four characteristics which togeter make a person a complete hypocrite, while anyone who has a trait among them possesses a trait of hypocrisy until he abandons it. They are - to betray a trust when entrusted, to lie when speaking,to break promises after making them and to use foul language when in an argument with others"
-Hadith : Sahih Bukhari and Sahin Muslim