Who am I permitted to shake hands with and who am I not permitted to?

Shaking hands with a non-mahram woman is not permissible, due to the statement of Aisha, may Allah be pleased with her: "By Allah, the hand of the Messenger of Allah (peace and blessings of Allah be upon him) never touched the hand of any woman," and due to the statement of the Messenger of Allah (peace and blessings of Allah be upon him): "For one of you to be stabbed in the head with an iron needle is better for him than to touch a woman who is not permissible for him." This ruling is agreed upon by the four imams concerning young and desirable women. Some scholars, however, have permitted shaking hands with an elderly woman if there is no fear of temptation.