Numan bin Bashir reported,

I heard the Messenger of Allah ﷺ say, "What is lawful is clear and what is forbidden is clear, and between the two are doubtful matters that many people do not know about. Whoever guards against these doubtful things keeps his religion and his honor above reproach, and whoever falls into them falls into what is forbidden. He is like a shepherd grazing his flock around a protected preserve, on the verge of letting them stray into it. Know that every king has a preserve, and Allah's preserve is what He has forbidden. Know too that within the human being there is a piece of flesh. When it is sound, the whole body is sound, and when it is corrupt, the whole body is corrupt. That piece of flesh is the heart."

وسمعت رسول الله ﷺ يقول إن الحلال بين والحرام بين وبينهما مشتبهات لا يعلمها كثير من الناس فمن اتقى الشبهات استبرأ فيه لدينه وعرضه ومن واقعها واقع الحرام كالراعي يرعى حول الحمى يوشك أن يرتع فيه ألا وإن لكل ملك حمى وإن حمى الله ما حرم ألا وإن في الإنسان مضغة إذا صلحت صلح الجسد كله وإذا فسدت فسد الجسد كله ألا وهي القلب