It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "The lawful is clear and the unlawful is clear, and between them are doubtful matters. Whoever falls into them is close to falling into sin, and whoever avoids them keeps his religion safer, like a person who grazes his animals beside a protected pasture: he is about to stray into it. Every king has a protected pasture, and the protected pasture of Allah is what He has made unlawful."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 10778