An explanation of the 1st hadith in the series on the Purification of the Heart:
The Messenger salla Allahi alayhi wa sallam said: (Halal is clear and haram is clear, and between the two are ambiguous matters that many people do not know their rulings. So whoever avoids the ambiguous matters will safeguard his religion and reputation. And the one who falls into them falls in the haram, like the shepherd who grazes around the sanctuary and is about to cross into it. Indeed, every king has a sanctuary and the sanctuary of Allah is His prohibitions. And indeed in the body there is a morsel of meat that if it is well, the rest of the body will be well; and if it is corrupt, then the rest of the body will be corrupt. It is the heart.) Reported by al-Bukhari and Muslim