It is narrated from Hazrat Nu'man (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: The example of the believer is like that of a body; if the head is in pain, the whole body feels the pain, and if the eye is in pain, the whole body feels the pain as well.
Hadith Referenceمسند احمد / أول مسند الكوفيين / 18393