According to historian Irfan Shahid, "it is almost certain" that the Banu al-Qayn, along with the Judham and Amila tribes, "functioned as military units in the Roman period, forming part of the Nabatean confederacy".[2] Moreover, Shahid argues the Banu al-Qayn dated back to the biblical era and "represent[ed] the strand of ethnographic continuity in the region, running from biblical to Byzantine to Muslim Arab times".[3] In the 4th century CE, the tribe's dwelling places were in Transjordan and they served as foederati (federates) of the Byzantine Empire.[4] They were among the Arab foederati, including the Banu Kalb, Judham, Bali, and Lakhm, that fought the Muslim Arabs at the Battle of Mu'tah in 629.[1][5] However, at least part of the Banu al-Qayn was on friendly terms with the Muslims for the latter had hoped for help from the Banu al-Qayn during the Battle of Chains that same year.[1] They again appear fighting for the Byzantines against the Muslims at the battles of Yarmouk and Fahl.[1]