During this period of his life he went on a journey to Persia for the purpose of confirming the faith of the Christians there, who were enduring persecutions under [[w:Shapur II|Shapur II]]. [[Theodoret of Cyrrhus|Theodoret]] records several miracles as taking place at this time.<ref>Theod. ''Vit. Patr.'' pp.1110 sq.)</ref> In addition, [[w:Gennadius of Massilia|Gennadius]] reports that Jacob was also a [[Saint titles|confessor]] during the [[w:Maximinus II (Daia)|Maximinian]] persecution as well.<ref>''de Script. Eccl.'' c.1.</ref>
After leading a severe life in the mountains of Kurdistan with St. [[w:Mar Awgin|Eugene (Augin)]], the founder of Persian monasticism, he became the second bishop of Nisibis in 309. Upon the vacancy of that see, which was his native city, Jacob was compelled by the demand of the people to become their bishop. He was then forced to exchange his desert life with life in the city. Although he moved to the city, he changed neither his food, nor his asceticism, nor his simple clothing. In his new position, he worked especially to help the oppressed, those in need, orphans, widows and the poor, for he greatly feared [[Jesus]], the Lord of Hosts.
:The bishop would not pray for the destruction of any one; but he implored the divine mercy that the city might be delivered from the calamities of so long a siege. Afterwards, going to the top of a high tower, and turning his face towards the enemy, and seeing the prodigious multitude of men and beasts which covered the whole country, he said: “Lord, thou art able by the weakest means to humble the pride of thy enemies; defeat these multitudes by an army of gnats.” God heard the humble prayer of his servant, as he had done that of [[Moses]] against the Egyptians, and as he had by the like means vanquished the enemies of his people when he conducted them out of Egypt. For scarcely had the saint spoken those words, when whole clouds of gnats and flies came pouring down upon the Persians, got into the elephants’ trunks, and the horses’ ears and nostrils, which made them chafe and foam, throw their riders, and put the whole army into confusion and disorder. A famine and pestilence which followed, carried off a great part of the army; and Sapor, after lying above three months before the place, set fire to all his own engines of war, and was forced to abandon the siege and return home with the loss of twenty thousand men.<ref name="BARTLEBY">[http://www.aol.bartleby.com/210/7/111.html St. James, Bishop of Nisibis, Confessor] at Bartleby.com.</ref>
'''School of Nisibis'''<br>
Around A.D. 350 St. Jacob founded the [[w:School of Nisibis|School of Nisibis]], after the model of the school of [[w:Diodorus of Tarsus|Diodorus of Tarsus]] in Antioch, in which he himself was an instructor. When the Persians conquered Nisibis in 363, the School moved to Edessa, where it operated from 363–489.