حَدَّثَنَا عَمْرُو بْنُ رَافِعٍ، حَدَّثَنَا عَبْدُ اللَّهِ بْنُ الْمُبَارَكِ، عَنْ زَكَرِيَّا بْنِ أَبِي زَائِدَةَ، عَنِ الشَّعْبِيِّ، قَالَ سَمِعْتُ النُّعْمَانَ بْنَ بَشِيرٍ، يَقُولُ عَلَى الْمِنْبَرِ وَأَهْوَى بِإِصْبَعَيْهِ إِلَى أُذُنَيْهِ سَمِعْتُ رَسُولَ اللَّهِ ـ صلى الله عليه وسلم ـ يَقُولُ ‏"‏ الْحَلاَلُ بَيِّنٌ وَالْحَرَامُ بَيِّنٌ وَبَيْنَهُمَا مُشْتَبِهَاتٌ لاَ يَعْلَمُهَا كَثِيرٌ مِنَ النَّاسِ فَمَنِ اتَّقَى الشُّبُهَاتِ اسْتَبْرَأَ لِدِينِهِ وَعِرْضِهِ وَمَنْ وَقَعَ فِي الشُّبُهَاتِ وَقَعَ فِي الْحَرَامِ كَالرَّاعِي حَوْلَ الْحِمَى يُوشِكُ أَنْ يَرْتَعَ فِيهِ أَلاَ وَإِنَّ لِكُلِّ مَلِكٍ حِمًى أَلاَ وَإِنَّ حِمَى اللَّهِ مَحَارِمُهُ أَلاَ وَإِنَّ فِي الْجَسَدِ مُضْغَةً إِذَا صَلُحَتْ صَلُحَ الْجَسَدُ كُلُّهُ وَإِذَا فَسَدَتْ فَسَدَ الْجَسَدُ كُلُّهُ أَلاَ وَهِيَ الْقَلْبُ ‏"‏ ‏.‏

While on the pulpit, pointing with this fingers towards his ears,Nu’man bin Bashir said: “I heard the Messenger of Allah (PBUH)say:‘That which is lawful is plain and that which is unlawful isplain,and between them are matters that are not clear, about whichnot manypeople know. Thus he who guards against the unclear matters,he clearshimself with regard to his religion and his honor. But hewho fallsinto the unclear matters, he falls into that which isunlawful. Likethe shepherd who pastures around a sanctuary, all butgrazing therein.Every king has a sanctuary. And beware! Allah’ssanctuary is Hisprohibitions. Beware! In the body there is a pieceof flesh which, ifit is sound, the whole body will be sound, and ifit is corrupt, thewhole body will be corrupt. It is the heart.’” Translation Not Available

Book Ref: Sunan Ibn Majah Book 36 Hadith 3984
Web Ref:  Sunan Ibn Majah Vol 5 Book 36 Hadith 3984