By the time of Jerome’s birth in the first half of the fourth century CE, the rabbinic Sages had become well accustomed to speaking of the bad yeṣer and the good yeṣer as constituent elements in the make-up of the individual human being. The two expressions are already found side by side at m. Ber. 9:5, interpreting Deut 6:5. Their place in what is an exegetical setting illustrates that the idea of the yeṣer had its home not in speculation, but in learned exposition of Scripture. While rabbinic writings later than the Mishnah continue to speak of both the good and the bad yeṣer, references to and discussion of the latter, simply designated “the yeṣer,” often predominate to the exclusion of the good yeṣer.