Hierarch Isaiah, Bishop of Rostov

Hierarch Isaiah was a native of the Kyiv lands; he was tonsured a monk at the Kyiv Caves Monastery under the guidance of Venerable Theodosius of the Caves. In 1062/1065, at the request of Prince Izyaslav, he became abbot of the Monastery of the Great Martyr Demetrius of Thessaloniki in Kyiv. No later than 1077/1078 he was consecrated Bishop of Rostov by Metropolitan John, becoming the successor to St. Leontius of Rostov.

As bishop he zealously preached among the pagan population of the Rostov-Suzdal land — destroying idols, building churches on the sites of former pagan shrines, and baptizing the inhabitants. He took part in the consecration of the Church of the Archangel Michael at the Vydubychi Monastery in 1088 and the Dormition Church of the Kyiv Caves Monastery in 1089.

He reposed in Rostov on May 15, 1090; he was buried in the Dormition Cathedral. His relics were found incorrupt during the cathedral's rebuilding (dated variously to 1162 or 1164) alongside those of St. Leontius, giving rise to popular veneration; his Life was composed in the 13th-15th centuries. Local veneration as a wonderworker was formally established in 1474 by Archbishop Vassian (Rylo).

IMPORTANT CONTAMINATION CORRECTION: the original stub erroneously listed "era: BC" and a date of "8th century BC" — this is direct contamination from the Old Testament Prophet Isaiah (who indeed lived in the 8th century BC), with whom St. Isaiah of Rostov has nothing in common besides the shared name. The commemoration date was also corrected: the original "May 9/22" is the feast day of the Prophet Isaiah specifically, not the Bishop of Rostov; the correct date is May 15/28.