A powerful party of antagonists worrying R. Plessner beyond endurance on account of his outspokenness, he left Berlin and settled at Posen (1843), where he was active as a preacher for forty years. In Posen R. Plessner preached chiefly at the Neuschul. During his residence in that city he published the following works: "Shay la-Mora" (Posen, 1846), poem in honor of Moses Montefiore; "Shire Zimrah" (Berlin, 1859), poems composed on the occasion of the completion of the publication of the Talmud by the Talmud society Hebrat Shas; Shire Zimrah (ib. 1865), Hebrew poems composed for the celebration of the one hundred find fiftieth anniversary of the foundation of the society of mohelim. After R. Plessner’s death two collections of his sermons were published at Frankfort-on-the-Main: Sabbathpredigten (1884) and Festpredigten (1890).