الْحَلَالُ بَيِّنٌ وَالْحَرَامُ بَيِّنٌ وَبَيْنَهُمَا مُشَبَّهَاتٌ لَا يَعْلَمُهَا كَثِيرٌ مِنْ النَّاسِ فَمَنْ اتَّقَى الْمُشَبَّهَاتِ اسْتَبْرَأَ لِدِينِهِ وَعِرْضِهِ وَمَنْ وَقَعَ فِي الشُّبُهَاتِ كَرَاعٍ يَرْعَى حَوْلَ الْحِمَى يُوشِكُ أَنْ يُوَاقِعَهُ أَلَا وَإِنَّ لِكُلِّ مَلِكٍ حِمًى أَلَا إِنَّ حِمَى اللَّهِ فِي أَرْضِهِ مَحَارِمُهُ أَلَا وَإِنَّ فِي الْجَسَدِ مُضْغَةً إِذَا صَلَحَتْ صَلَحَ الْجَسَدُ كُلُّهُ وَإِذَا فَسَدَتْ فَسَدَ الْجَسَدُ كُلُّهُ أَلَا وَهِيَ الْقَلْبُ
Verily, the lawful is clear and the unlawful is clear, and between the two of them are doubtful matters about which many people do not know. Thus, he who avoids doubtful matters clears himself in regard to his religion and his honor, and he who falls into doubtful matters will fall into the unlawful as the shepherd who pastures near a sanctuary, all but grazing therein. Verily, every king has a sanctum and the sanctum of Allah is His prohibitions. Verily, in the body is a piece of flesh which, if sound, the entire body is sound, and if corrupt, the entire body is corrupt. Truly, it is the heart.
Ṣaḥīḥ al-Bukhārī 52, Grade: Muttafaqun Alayhi