In 1524, under the influence of his Biblical studies, he wrote to Duke Johann Frederick of Saxony, praising the institution of tithes and even of fifths: “It would be a grand thing if, according to ancient usage, a tenth of all property were annually handed over to the authorities; this would be the most Godly interest possible.… Indeed it would be desirable to do away with all other taxes and impose on the people a payment of a fifth or sixth, as Joseph did in Egypt.”[255] At the same time he is quite aware that such wishes are impracticable, seeing that, “not the Mosaic, but the Imperial law is now accepted by the world and in use.” Partly owing to the impossibility of a return to the Old Covenant, partly out of a spirit of contradiction to the new party, he opposed the fanatics’ demand that the Mosaic law should be introduced as near as possible entire, and the Imperial, Roman law abrogated as heathenish and the Papal, Canon law as anti-Christian. Duke Johann, the Elector’s brother, was soon half won over to these fantastic ideas by the Court preacher, Wolfgang Stein, but Luther and Melanchthon succeeded in making him change his mind.[256] The necessity Luther was under of opposing the Anabaptists here produced its fruits; his struggle with the fanatics preserved him from the consequences of his own personal preference for the social regulations of the Old Covenant. In what difficulties his Old-Testament ideas on polygamy involved him the history of the bigamy of Philip of Hesse has already shown.[257] Had such ideas concerning marriage been realised in society the revolution in the social order would indeed have been great. Luther’s esteem for the social laws of the Old Testament finds its best expression in his sermons on Genesis, which first saw the light in 1527. He says, for instance, of the Jewish law of restitution and general settlement of affairs, in the Jubilee Year: “It is laid down in Moses that no one can sell a field in perpetuity but only until the Jubilee Year, and when this came each one recovered possession of his field or the property he had sold, and thus the lands remained in the family. There are also some other fine laws in the Books of Moses which well might be adopted, made use of and put in force.” He even wishes that the Imperial Government would take the lead in re-enacting them “for as long as is desired, but without compulsion.”[258] His views on interest and usury were likewise influenced by his one-sided reading of certain Old- and New-Testament statements. _Usury and Interest_