This article is the first to focus on statements about ethical guidance in post-classical astronomy texts. A number of astronomers in post-classical Islamic societies remarked that the study of astronomy, specifically the mathematical analysis of the uniform motions of the celestial orbs, had ethical benefits. These astronomers’ statements are significant because, through them, scholars can learn more about the role of reason in Islamic thought and about sources of ethical guidance other than Sharīʿa and philosophical ethics. The details of the ethical guidance imparted by the study of astronomy tell us more about the relationship between astronomy and the disciplines of fiqh and kalām, respectively. The existence of ethical guidance in astronomy texts is additional evidence that post-classical astronomy texts were part of an Islamic intellectual tradition.