Sunan ad-Darimi

Sayyiduna Nu’man bin Bashir (may Allah be pleased with both of them) says: I heard the Messenger of Allah (peace and blessings be upon him) say: “The lawful is clear and the unlawful is also clear, and between the two are some doubtful matters (whose lawfulness or unlawfulness is not known to everyone); many people do not know about them (whether they are lawful or unlawful). So whoever avoids doubtful matters has protected his religion and his honor, and whoever falls into doubtful matters will fall into the unlawful. The example of this is like a shepherd who grazes his animals around a (royal protected) pasture, so it is likely that he may enter it (and be considered a royal offender). Listen! Every king has a protected pasture, and the protected pasture of Allah on His earth is His unlawful things (so avoid them). Listen! There is a piece of flesh in the body; when it is sound, the whole body is sound, and when it is corrupt, the whole body is corrupt. Listen! That piece is the heart (of a person).”