According to the Catholic Church describe the connection between purgatory in the selling of indulgences

Raising the mind to God with humble trust while performing one's duties and bearing life's difficulties, and adding, at least mentally, some pious invocation. Devoting oneself or one's goods compassionately in a spirit of faith to the service of one's brothers and sisters in need. Freely abstaining in a spirit of penance from something licit and pleasant. Freely giving open witness to one's faith before others in particular circumstances of everyday life.