This Prophet (whose name means “who is like God?”), was a Morasthite from the land of Judah. He prophesied more than fifty years in the days of Joatham, Ahaz, and Hezekias, Kings of Judah. These kings reigned in the eighth century before Christ. From this it is clear that this Michaias is not the one who was the son of Iembla (or Imlah-III Kings 22:8), who censured Ahab and was murdered by Ahab’s son Joram, as the Synaxaristes says; for this Joram reigned the ninth century before Christ. Yet Michaias was still prophesying, as mentioned above, in the days of Hezekias, who was a contemporary of Hosea and Esaias, and of Hoshea, the last King of the ten tribes of Israel, when that kingdom was destroyed by Salmanasar (Shalmaneser), King of the Assyrians (IV Kings 17: 1 – 16; 18: 1). This Michaias is sixth in rank among the minor Prophets. His book of prophecy is divided into seven chapters; he prophesied that the Christ would be born in Bethlehem (Michaias 5: 2). In the reign of Saint Theodosius the Great, the holy relics of the Prophets Michaias and Abbacum were found through a divine revelation to Zebennus, Bishop of Eleutheropolis (Sozomen, Eccl. Hist., Book VII, 29).
From www.goarch.org