Among the Thirteen Assyrian Fathers
Isidore belonged to the group of monastic missionaries remembered in Georgian church history as the Thirteen Assyrian (Syrian) Fathers, who arrived from the East to strengthen Christianity in Georgia during the sixth century. The tradition names John of Zedazeni as their leader; he had received his spiritual formation in Antioch and, according to the synaxarion, was directed by the Mother of God to take twelve monks and go to Georgia. Georgian church historians credit the Fathers as a whole with founding several monasteries and hermitages and with initiating the ascetic movement in the country.
The synaxarion relates that while the Fathers were in Mesopotamia on their way to Georgia, King Parsman and Catholicos Evlavios received news of their coming and met them at Mtskheta. With the blessing of the Catholicos the monks first settled on Zedazeni Mountain, the site of a former pagan temple, after which they were sent out across the kingdom to preach. Each of the disciples became linked to a particular place and monastic foundation. Scholars note that the surrounding tradition names as many as nineteen Assyrian monks active in sixth-century Georgia, and that the number 'thirteen' appears to be largely symbolic.