“Erasmus laid the egg, Luther hatched it.” Already in the early Reformation this popular quip suggested a direct, causal link between humanism and the Protestant Reformation. Yet Luther’s precise debt to Erasmus has remained an elusive problem. This article reconsiders the issue by investigating how Luther read Erasmus’s scholarship, focusing on two remarkable, little-studied examples: Erasmus’s edition of Jerome and his Annotations to the New Testament. Luther’s annotated copies reveal a deep ambivalence toward the humanist and a distinctly uncharitable reading style. Although Luther diligently collected welcome information, he excoriated what he regarded as Erasmus’s desacralizing philological perspective and his malicious use of humor. Luther’s perception of Erasmian humor in fact operated as an interpretative tool that enabled him to project his suspicions about Erasmus’s skepticism and unbelief into the text. Documenting Luther’s continued preoccupation with Erasmus, this article offers a reevaluation of Erasmus’s intellectual significance for Luther’s theological development.