How can we tell whether a good deed is truly done for the sake of Heaven?

This source-based Hagut Yosef essay explores the question: How can we tell whether a good deed is truly done for the sake of Heaven? The canonical Hebrew article develops the theme through Torah sources and reflection on human life. This localized discovery layer preserves the meaning and source identity; it does not add a new halakhic, historical, psychological, medical, legal, or empirical claim beyond the Hebrew source.