Qos (Edomite: 𐤒𐤅𐤎 Qāws; Hebrew: קוש Qōš, also Qōs, Qaus, Koze) was the national god of the Edomites. He was the Idumean rival of Yahweh, and structurally parallel to him. Thus ‘Benqos’ (son of Qōs) parallels the Hebrew ‘Beniyahu’ (son of Yahweh). The name occurs only once in the Old Testament (if we exclude a possible allusion in an otherwise corrupted text in the Book of Proverbs) in the Book of Ezra as an element in a personal name, Barqos ('Qōs gleamed forth'), referring to the 'father' of a family or clan of perhaps Edomite/Idumaean nĕtînîm or temple helpers returning from the Babylonian exile. The noun frequently appears combined with names on documents recovered from excavations in Elephantine, where a mixed population of Arabs, Jews and Idumeans lived under the protection of a Persian-Mesopotamian garrison.
The name "Qos" is never mentioned on its own in the Tanakh in relation to the Edomite deity, however it does unambiguously appear twice as an element in a person name in Ezra 2:53 and Nehemiah 7:55 as Barqos, "son of Qos". Qos may appear in a similar fashion in a personal name in 1 Chronicles 15:17 rendered as Kushaiah where it would mean "Qos is Yahweh", however the element conjectured to represent "Qos" is pronounced differently and thus the name has been understood to mean "bow of Yahweh" instead. Qōs itself may mean bow. Unlike the chief god of the Ammonites (Milkom) and the Moabites (Chemosh), the Tanakh refrains from explicitly naming the Edomite Qōs and Yahweh hailed from Se'ir in the region of Edom. The omission may be explained, according to some scholars, by the close similarity of Yahweh with Qōs, making rejection of the latter difficult. Both Qōs and Yahweh are probably words of Arabic origin, and Knauf and others argue that YHWH is a northern Arabic word, from the Semitic root hwy, meaning "he blows". Knauf concludes that the two are typologically similar, being "forms of the Syrian-Arabian weather-god, among whose attributes the bow is as much a part of as the storm."
Recently the view has been advanced that Yahweh was originally an Edomite/Kenite god of metallurgy. According to this approach Qōs might possibly have been a title for Yahweh, rather than a name. A further point connecting Yahweh with Qōs, aside from their common origin in that territory, is that the Edomite cult of the latter shared characteristics of the former. Thus we find that Dō’êḡ the Edomite has no problem in worshiping Yahweh, he is shown to be at home in Jewish sanctuaries, circumcision was practiced in Edom. Additionally, supplication of Yahweh isn't uncommon where mentions of Qos are lacking, a pottery sherd from the late 9th/early 8th centuries BCE at Kuntillet Ajrud blesses its recipient by "Yahweh of Teman", which some have taken as implying that, at least from an Israelite perspective, Qos and Yahweh were considered identical, though it by no means necessarily proves it. Additionally, there are some discrepancies which make a direct association between the two difficult. Oded Balaban, for instance, argued in 1971 that certain names found on Ramesside topographical lists are theoporic and contain references to Qos, which if true would put the deity's earliest attestation more than 600 years before Yahweh's.
Qōs became identified with Quzah, "the archer" in the north Arabian pantheon, worshiped both as a mountain and a weather god. The similarity of the name would have permitted an assimilation of Qōs to the Arabian god of the rainbow, qaws quzaḥ.
The worship of Qōs appears to originally have been located in the Ḥismā area of southern Jordan and north Arabia, where a mountain, Jabal al-Qaus, still bears that name. He entered the Edomite pantheon as early as the 8th century b.c. M. Rose speculates that, prior to Qōs's advent, Edom worshipped Yahweh—a connection going back the early Egyptian references to YWH in the land of the Shasu—and the former then overlaid the latter and assumed supremacy there when the Idumeans lost their autonomy under Persian rule, perhaps compensating for the destruction of national independence, a mechanism similar to that of the strengthening of Yahweh worship after the fall of the Jewish kingdom. Qōs is described as a "King", is associated with light, and defined as "mighty". His works are described as ones where he "adorns, avenges, blesses, chooses(?) gives."
Costobarus I, whose name meant "Qōs is mighty" was a native Idumean descended from a priestly family attached to this cult. After Herod, had placed him in command over (στρατηγὀς) Idumea, Costobarus, supported by Cleopatra, eventually tried to prise the kingdom from Herod's Judea. In order to garner local support for his defection, he revived the old cult of Qōs, perhaps to get Idumea's rural population, still attached to its traditional gods, to back him. The name recurs in the Nabataean language in an inscription at Khirbet et-Tannur, where he is represented flanked by bulls, seated on a throne while wielding in his left hand a multi-pronged thunderbolt, suggestive of a function as a weather god. He is also on an altar in Idumean Mamre.
The deity's name was used as the theophoric element in many Idumean names, including the names of the Edomite kings Qōs-malaku, a tributary of Tiglath-Pileser III and Qōs-gabar a tributary of Esarhaddon.