Is it permissible for a man to wash his mother (for burial)?

It is not permissible for a man to wash a woman, even if she is one of his mahārim (unmarriageable kin) like his mother or daughter. The only exception is a wife, who may wash her husband, and vice-versa. Men are to be washed by men, and women by women. An exception to this is children under the age of seven, where it is permissible for a woman to wash a boy and for a man to wash a girl.