He was born about 550 probably at Damascus. He was given the epithet "ὁ ἐγκρατής". He lived successively with the monks at the monastery of St. Theodosius southeast of Jerusalem, among the hermits in the Jordan Valley, and in the New Lavra of St. Sabbas the Sanctified near Teqoa, east of Bethlehem. About the year 578 he went to Egypt with Sophronius and came as far as the Great Oasis of the Libyan Desert. After 583 he came to Mount Sinai and spent about ten years in the Lavra of the Aeliotes; he then visited the monasteries near Jerusalem and the Dead Sea. In 604 he went to Antioch but returned to Egypt in 607. Later he went to Cyprus and in 614-615 to Rome, where he died in 619. On his deathbed he requested Sophronius to bury him, if possible, on Mt. Sinaior else at the Monastery of St. Theodosius near Jerusalem. Mt. Sinai being then invaded by the Saracens, Sophronius buried him at St. Theodosius. John Moschus' feast day in the Eastern Orthodox Church is shared with that of Sophronius.
He is the author of one of the earliest hagiological works, entitled in Greek "Leimōn pneumatikos" and known in Latin as "Pratum spirituale", occasionally abbreviated "Prat. Spirit.", also quoted as the Leimonarion, or as the "New Paradise", which he wrote during the 610s or 20s. In it he narrates his personal experiences with many great ascetics whom he met during his extensive travels, mainly through Palestine, Sinai and Egypt, but also Kilikia and Syria, and repeats the edifying stories which these ascetics related to him. The work teems with miracles and ecstatic visions and it gives a clear insight into the practices of Eastern monasticism, contains important data on the religious cult and ceremonies of the time, and acquaints us with the numerous heresies that threatened to disrupt the Church in the East. It was first edited by Fronton du Duc in Auctarium biblioth. patrum, II, 1057–1159. A better edition was brought out by Cotelier in Ecclesiae Graecae Monumenta, II, which is reprinted in J.-P. Migne, Patrologia Graeca. LXXXVII, III, 2851–3112. A Latin translation, by Ambrose Traversari, is printed in Migne, Patrologia Latina, LXXIV, 121–240, and an Italian version made from the Latin of Traversari.
Conjointly with Sophronius, Moschus wrote a life of John the Almoner, a fragment of which is preserved in the first chapter of the "Vita S. Joanni Eleemosynarii" by Leontios of Neapolis, under the name of Simeon Metaphrastes.
