The work presented here for the first time in a Spanish translation -- the *Kitāb fī al-jimā'*, or *Treatise on Coitus* -- was written in 12th-century Egypt at the request of a high-ranking dignitary, whom Maimonides addresses with the respectful title "the most honored Lord." This figure, the owner of numerous female slaves, sought a regimen that would allow him to maintain or enhance his sexual potency without compromising his health. Far from providing an erotic manual, Maimonides offers a strictly medical treatise: a text that approaches sexuality through the lenses of physiology, psychology, and hygiene. *Treatise on Coitus* is a medical work on sexual vigor -- commissioned by a high official -- in which the author argues that diet is more effective than medication and that the organs must be kept "warm and moist." It innovatively highlights the importance of psychological factors: joy and rest foster desire, whereas sadness or aversion severely impair it. Maimonides recommends specific foods and wine to strengthen the body, offers recipes and remedies, and rounds out the regimen with guidelines on hygiene, massage, and lifestyle habits aimed at preserving health and serving God. The work enjoyed widespread circulation during the Middle Ages thanks to translations into Hebrew, Latin, and Church Slavonic, facilitating its spread across Jewish and Christian communities and even its incorporation into the *Secretum Secretorum*. It was cited as an authoritative source by physicians and encyclopedists alike. Its influence was also notable for the central role it assigned to psychological factors in sexuality -- an approach rarely seen in Western medicine at the time.