The monastery was founded in 363 by the hermit Mar Mattai who had fled persecution in Amid under the Roman Emperor Julian the Apostate. According to Syriac tradition, he was involved in healing the sister of Mor Behnam and converting the brother and sister to Christianity. Their father, King Sinharib of Assyria initially killed his son and daughter but later recanted and awarded Mattai a place atop Mount Alfaf to establish his monastery. Mattai was quickly joined by a small group of Syriac followers, and under his leadership that community developed a true monastic ethos.