The paper in its introductory part offers a brief biography of the famous Ġassānid ruler in the opposition to his archenemy, the Laḫmid king Al-Munḏir III. The core of the article is nevertheless the presentation of a battle which changed the position of the conflicting kingdoms in favor of Al-Ḥāriṯ and his successors. The present article aims to collect the main medieval sources describing the battle of Qennešrīn. Syriac, Greek and Arabic texts have been chosen, translated and analyzed. The Syriac sources, although limiting the data to just a few sentences, bring the most important facts such as the place and the date of the battle, names of the warriors and the later repercussions of the combat. The Greek texts are hagiographical but they also corroborate the names of antagonists and add a few details concerning the progress of the battle. The Arabic sources are then most challenging; even though they bring a very detailed description of the battle, the genealogies of the warriors and their allies, the researchers still have to untangle the manifold and sometimes erroneous lists of names involved in the historical or alleged battles, to rearrange the facts according to the external sources and to dismiss the tempting, but most probably apocryphal, accounts even though they have found their place in popular academic textbooks.