From the route of Abu ^Abdillah an-Nu^man bin Bashir, may Allah accept both of their deeds, who said: I heard the Messenger of Allah, sallallahu ^alayhi wa sallam, say:
<<The lawful matters are clearly stated and the forbidden matters are clearly stated. And in between them there are matters that many people do not know the judgment of. Hence, the one who avoids falling into questionable matters would protect his religiosity and integrity.
The one who falls into the questionable matters will fall into the unlawful, just like the shepherd grazing his flock around a fenced property and who very likely will crossover into it. Indeed, every king has his own protected property and indeed, the boundaries that Allah ordered not to be violated are the forbidden matters.
Indeed, there is a bloody small part in the body when it is sound, the entire body will be sound, and if it is spoiled, the entire body will be spoiled. Indeed, it is the heart.>>
Narrated by al-Bukhari and Muslim.