Abraham ha-Yakini was one of the chief agitators in the Sabbatean movement, the son of Pethahiah of Constantinople. He was born—according to a not entirely reliable source, מאורעות צבי (Lemberg, 1871, p. 3)—on September 8, 1611. He studied under Joseph di Trani of Constantinople (died 1644), and under Mordecai, a German kabalist. From the latter he probably derived the touch of mysticism which, combined with cunning and great intelligence, made him the most suitable representative of Sabbatai Zevi. Ha-Yakini persuaded Sabbatai Zevi, who at that time was convinced that he was the Messiah but was timid and fearful of proclaiming himself, boldly to declare his claims. It was in Constantinople, about 1653, that Sabbatai Zevi became acquainted with Ha-Yakini, who, on account of his learning and