Hadith #255
Roman (Roman Urdu)Verily, there is a piece of flesh in the body; when it is rectified, the entire body is rectified, and when it gets spoiled, the whole body gets spoiled; beware! that is the heart.
Reference: صحيح البخاري، كتاب الإيمان، باب فضل من استبرأ لدينه، الحدیث 52