Al - Harith ibn Jabalah Al - Ḥārith ibn Jabalah ( ) , [ Flavios ] Arethas ( ) in Greek sources and Khālid ibn Jabalah ( ) in later Islamic sources , was a king of the Ghassanids , a pre - Islamic Arab people who lived on the eastern frontier of the Byzantine Empire . The fifth Ghassanid ruler of that name , he reigned from circa 528 to 569 and played a major role in the wars with Persia and the affairs of the Monophysite Syriac Church . For his services to Byzantium , he was made a " patricius " and a " gloriosissimus " . Biography . Early life . Harith was the son of Jabalah ( Gabalas in Greek sources ) and brother of Abu Karib ( Abocharabus ) , phylarch of Palaestina Tertia . He became ruler of the Ghassanids and phylarch of Arabia Petraea and Palaestina Secunda probably in 528 , following the death of his father in the Battle of Thanuris . Soon after ( circa 529 ) he was raised by the Byzantine emperor Justinian I ( r . 527 – 565 ) , in the words of the historian Procopius , " to the dignity of king " , becoming the overall commander of all the Empire ' s Arab allies ( " foederati " ) in the East with the title of " patrikios " ( , " patrician and phylarch of the Saracens " ) . His actual area of control , however , may initially have been limited to the northeastern part of Byzantium ' s Arab frontier . At the time , the Byzantines and their Arab allies were engaged in a war against the Sassanid Persians and their Arab clients , the Lakhmids , and Justinian ' s move was designed to create a counterpart to the powerful Lakhmid ruler , Mundhir , who controlled the Arab tribes allied to the Persians . Military career . In this capacity , Harith fought on behalf of the Byzantines in all their numerous wars against Persia . Already in 528 he was one of the commanders sent in a punitive expedition against Mundhir . In 529 , he helped suppress the wide - scale Samaritan revolt , capturing 20 , 000 boys and girls whom he sold as slaves . It was perhaps Harith ' s successful participation in this conflict that led Justinian to promote him to supreme phylarch . It is possible that he took part with his men in the Byzantine victory at Daras in 530 , although no source explicitly mentions him . In 531 , he led a 5 , 000 - strong Arab contingent in the Battle of Callinicum . Procopius , a source hostile to the Ghassanid ruler , states that the Arabs , stationed on the Byzantine right , betrayed the Byzantines and fled , costing them the battle . John Malalas , however , whose record is generally more reliable , reports that while some Arabs indeed fled , Harith stood firm . The charge of treason levelled by Procopius against Harith seems to be further undermined by the fact that , unlike Belisarius , he was retained in command and was active in operations around Martyropolis later in the year . In 537 / 538 or 539 , he clashed with Mundhir of the Lakhmids over grazing rights on the lands south of Palmyra , near the old " Strata Diocletiana " . According to later accounts by Tabari , the Ghassanid ruler invaded Mundhir ' s territory and carried off rich booty . The Persian ruler , Khosrau I ( r . 531 – 579 ) , used this dispute as a pretext for restarting hostilities with the Byzantines , and renewed war broke out in 540 . In the campaign of 541 , Harith and his men , accompanied by 1200 Byzantines under generals John the Glutton and Trajan , were sent by Belisarius into a raid into Assyria . The expedition was successful , penetrated far into enemy territory and gathered much plunder . At some point , however , the Byzantine contingent was sent back , and subsequently Harith failed to either meet up with or inform Belisarius of his whereabouts . According to Procopius ' s account , this , in addition to the outbreak of a disease among the army , forced Belisarius to withdraw . Procopius further alleges that this was done deliberately so that the Arabs would not have to share their plunder . In his " Secret History " , however , Procopius gives a different account of Belisarius ' s inaction , completely unrelated to the Ghassanid ruler . In circa 544 / 545 , Harith was involved in armed conflict with another Arab phylarch , al - Aswad , known in Greek as Asouades . From circa 546 on , while the two great empires were at peace in Mesopotamia after the truce of 545 , the conflict between their Arab allies continued . In a sudden raid , Mundhir captured one of Harith ' s sons and had him sacrificed . Soon after , however , the Lakhmids suffered a heavy defeat in a pitched battle between the two Arab armies . The conflict continued , with Mundhir staging repeated raids into Syria . In one of these raids , in June 554 , Harith met him in the decisive Battle of Yawm Halima ( the " Day of Halima " ) , celebrated in pre - Islamic Arab poetry , near Chalcis , at which the Lakhmids were defeated . Mundhir fell in the field , but Harith also lost his eldest son Jabalah . In November 563 , Harith visited Emperor Justinian in Constantinople , to discuss his succession and the raids against his domains by the Lakhmid ruler ' Amr , who was eventually bought off by Justinian . He certainly left a vivid impression in the imperial capital , not least by his physical presence : John of Ephesus records that years later , the Emperor Justin II ( r . 565 – 578 ) , who had descended into madness , was frightened and went to hide himself when he was told " Arethas is coming for you " . Death . When al - Harith died in 569 , possibly during an earthquake , he was succeeded by his son al - Mundhir ( Alamoundaros in Byzantine sources ) . Taking advantage of this , the new Lakhmid ruler Qabus launched an attack , but was decisively defeated . Religious policies . In contrast to his Byzantine overlords , Harith was a staunch Monophysite and rejected the Council of Chalcedon . Throughput his rule , al - Harith supported the anti - Chalcedonian tendencies in the region of Syria , presiding over church councils and engaging in theology , contributing actively to the Monophysite church ' s revival during the 6th century . Thus in 542 , following two decades of persecutions which had decapitated the Monophysite leadership , he appealed for the appointment of new Monophysite bishops in Syria to the Empress Theodora , whose own Monophysite leanings were well - known . Theodora then appointed Jacob Baradaeus and Theodore as bishops . Jacob in particular would prove a very capable leader , converting pagans and greatly expanding and strengthening the organization of the Monophysite church .