He was a faster and fellow ascetic of St. Euthymius the Great. Theoctistus was abbot of Euthymius’s Lavra, located some six miles from Jerusalem on the road to Jericho. In all things he was a disciple of St. Euthymius under whose spiritual guidance he governed the monastery until the age of ninety. He pleased God by his life, and reposed in the middle of the fifth century during the reign of Anastasius, Patriarch of Jerusalem.