Both the Lawful and Unlawful matters are clear

An-Nu`man bin Bashir (Radhi Allahu Anhu) said that he heard the Messenger of Allah (Sallallahu Alayhi wa Sallam) say,

Both lawful and unlawful things are evident, but in between them there are matters that are not clear. So whoever saves himself from these unclear matters, he saves his religion and his honor. And whoever indulges in these unclear matters, he will have fallen into the prohibitions, just like a shepherd who grazes (his animals) near a private pasture, at any moment he is liable to enter it. (Al-Bukhari and Muslim)