His _De Rudimentis Hebraicis_, [Sidenote: 1506] a grammar and dictionary of this language, performed a great service for scholarship.

In the late Jewish work, the _Cabbala_, he believed he had discovered a source of mystic wisdom.

The extravagance of his interpretations of Scriptual passages, based on this, not only rendered much of his work nugatory, but got him into a great deal of trouble.

The converted Jew, John Pfefferkorn, proposed, in a series of pamphlets, that Jews should be forbidden to practise usury, should be compelled to hear sermons and to deliver up all their Hebrew books to be burnt, except the Old Testament.

When Reuchlin's aid in this pious project was requested it was refused in a memorial dated October 6, 1510, pointing out the great value of much Hebrew literature.