Jacob was born at Nisibis (''Antiochia Mygdoniae'') towards the end of the third century. According to St. [[w:Mar Awgin|Eugene (Augin)]],<ref group="note">"...tradition ascribes Persian monasticism to a certain [[w:Mar Awgin|Eugene (Augin)]], who brought it from the Egyptian desert, and founded the famous monastery of [[w:Mount Izla|Mount Izla]] near Nisibis in the early 4th century." (Fr. Dr. [[w:Adrian Fortescue (priest)|Adrian Fortescue]]. ''[http://www.archive.org/details/lessereasternchu00fortuoft Lesser Eastern Churches].'' London: Catholic Truth Society, 1913. p.43.)</ref> the holy St. Jacob came from the tribe and the family of [[Apostle James the Just|St. James the brother of the Lord]].<ref name="ASOC">[[Church of Antioch (Syriac)|Antiochian Syriac Orthodox Church]]. ''[http://syrorthodoxchurch.com/english-Dateien/Page2149.htm St. Jacob of Nisibis].''</ref> By some accounts he is said the have been nearly related to [[Gregory the Enlightener|Gregory the Illuminator]], the Apostle of Armenia.<ref group="note">However according to Jacob's biographical entry at CCEL: "The Armenians mistakenly call him the friend of Gregory the Illuminator." (Christian Classics Ethereal Library (CCEL). ''[http://www.ccel.org/s/schaff/encyc/encyc06/htm/iii.lv.xvi.htm JACOB (JAMES) OF NISIBIS].'')</ref>
At an early age he devoted himself to the [[Monasticism|life of a solitary]], practicing the severest [[Asceticism|self-discipline]].<ref group="note">The celebrity that Jacob acquired by the strictness of his [[asceticism]] and his spiritual gifts, caused [[Theodoret of Cyrrhus|Theodoret]] to assign him the first place in his ''Religiosa Historia'' or ''Vitae Patrum'' - where he is entitled '''"Ο μέγας"''' ('''"the great"''') - in which his self-imposed austerities, and the miracles of which he was the reputed worker, are fully detailed.</ref> He liked the solitude and the peace of the [[Desert Fathers|desert]], and he lived in the mountains. In the summer he lived in crevices of the mountains, and in the winter he lived for a short time in a cave. His food was not what he had sown, but what grew there on its own, such as fruits from wild trees and green plants that grew in the desert. His clothing was made of hard goat's hair.
He always fed on spiritual food which came through [[prayer]] which also kept his thoughts pure. Through his asceticism, he gained a deeper connection with God. He had the gift of foresight, and by the grace of the [[Holy Spirit|Spirit]], he received the gift of miracles.