The Decades (Hausbuch / Fifty Sermons in Five Decades)
Heinrich Bullinger, Zwingli's successor in Zurich, published his fifty Decades between 1549 and 1551 as a systematic pastoral theology in sermon form, covering the Apostles' Creed, the Decalogue, prayer, the sacraments, and Christian governance. In England, Archbishop Whitgift obtained a 1586 Convocation order requiring every clergyman without a theology degree to own and read one sermon from the Decades weekly, making it the closest thing the Elizabethan church had to a mandatory devotional reading program. Bullinger's correspondence of over 12,000 letters to princes, theologians, and pastors across Reformed Europe further extended its reach into court and household use from Zurich to London. Its influence on the English Reformed tradition rivals that of Calvin's Institutes in shaping Elizabethan clergy formation.