Sayyiduna Bashir bin Sa'd (may Allah be pleased with him), who was a Companion of the Prophet (peace and blessings be upon him), narrated: the Prophet (peace and blessings be upon him) said: "The position of one believer in relation to another believer is like the position of the head in relation to the body. When the body is in pain, the head also feels pain because of it, and when the head is in pain, the whole body feels pain."
Al-Tabarani recorded it; its chain contains a narrator, Abdullah al-Madini, who is matruk (abandoned).