Numan bin Bashir reported,

He said, "I heard the Messenger of Allah ﷺ say," and Numan pointed with his two fingers toward his ears, "'The lawful is clear, and the unlawful is clear, and between them are doubtful matters that many people do not know. Whoever guards against doubtful matters protects his religion and his honor, and whoever falls into doubtful matters falls into the unlawful, like a shepherd grazing his flock around a protected sanctuary, on the verge of letting them graze within it. Truly, every king has a sanctuary, and truly, the sanctuary of Allah is what He has forbidden. Truly, in the body there is a morsel of flesh which, when sound, makes the whole body sound, and when corrupt, makes the whole body corrupt. Truly, it is the heart.'"

عن النعمان بن بشير

قال سمعت رسول الله ﷺ يقول (وأهوى النعمان بإصبعيه إلى أذنيه): إن الحلال بين، وإن الحرام بين، وبينهما مشتبهات لا يعلمهن كثير من الناس، فمن اتقى الشبهات استبرأ لدينه وعرضه، ومن وقع فى الشبهات وقع في الحرام، كالراعي يرعى حول الحمى يوشك أن يرتع فيه. ألا وإن لكل ملك حمى، ألا وإن حمي الله محارمه، ألا وإن في الجسد مضغة إذا صلحت صلح الجسد كله، وإذا فسدت فسد الجسد كله ألا وهى القلب.