What is the ruling on handshaking in Islam?

The Prophet, peace and blessings be upon him, encouraged men to shake hands with men, women with women, and a man with his mahram (definition). This is a recommended act, as stated in the Hadith (definition): "There are no two Muslims who meet and shake hands but they are forgiven before they part." As for shaking hands with non-mahram individuals, it is not permissible. This is indicated by the Hadith: "For one of you to be stabbed in the head with an iron needle is better for him than that he should touch a woman who is not permissible for him," and by Aishah's statement: "The hand of the Messenger of Allah, peace and blessings be upon him, never touched the hand of a woman at all."