We read in the Talmud that a Gentile once came to Shamai and said, "How
many laws have you?" Shamai replied, "We have two, the written law and
the oral law." To which the Gentile made answer, "When you speak of the
written law, I believe you, but in your oral law I have no faith.
Nevertheless, you may make me a proselyte on condition that you teach me
the written law only." Upon this Shamai rated him sharply, and sent him
away with indignant abuse. When, however, this Gentile came with the
same object, and proposed the same terms to Hillel, the latter proceeded
at once to proselytize him, and on the first day taught him Aleph, Beth,
Gemel, Daleth. On the morrow Hillel reversed the order of these letters,
upon which the proselyte remonstrated and said, "But thou didst not
teach me so yesterday." "True," said Hillel, "but thou didst trust me in
what I taught thee then; why, then, dost thou not trust me now in what I
tell thee respecting the oral law?"
THE TALMUD, _Shabbath_, fol. 31, col. 1.