Crusade-era prophecy recycled the biblical cycle of sin and deliverance.

Evidence

The prophecy goes on to say that a succession of forty Christian kings will rule in peace and tranquility, after which Christian sins will bring on the reign of Antichrist. This new prediction fits the pattern Fidentius outlined at the outset of the Liber recuperationis: an alternation between peaceful rule by God’s people and upheaval caused by the sins of his people. — John V. Tolan, Saracens, 1089