The respect from host to guest. The host must be hospitable to the guest and provide them with food and drink and a bath, if required. It is not polite to ask questions until the guest has stated their needs. The respect from guest to host. The guest must be courteous to their host and not be a burden. The parting gift (xenion, ξεινήιον) from host to guest. The parting gift is to show the host's honor at receiving the guest. Xenia was considered to be particularly important in the ancient times when people thought gods mingled amongst them. If you had played host to a deity (a concept known as theoxenia) and performed poorly, you would incur the wrath of a god. It is thought that the Greek practice of theoxenia may have been the antecedent of the Roman rite of Lectisternium, or the draping of couches. The policy of Xenia also includes the protection of travelling bards. They would receive hospitality in the form of a place to sleep, food, and often an assortment of gifts in turn for entertainment and news from other parts of the ancient world. The safety of these bards was believed to have been secured by the aegis-wielding Zeus, and any violation of xenia would put the violator at the mercy of either Zeus or any lower god that he saw fit to enforce the unwritten code. In the Iliad
The Trojan war described in the Iliad of Homer actually resulted from a violation of xenia. Paris, from the house of Priam of Troy, was a guest of Menelaus, king of Mycenaean Sparta, but seriously transgressed the bounds of xenia by abducting his host's wife, Helen. Therefore the Achaeans were required by duty to Zeus to avenge this transgression, which as a violation of xenia was an insult to Zeus's authority. Diomedes and Glaucus meet in battle and before attacking, the former asks the lineage of the latter. Glaucus tells his lineage, upon which Diomedes realizes their guest-friendship.