This note identifies Jerome's commentary on Paul's Epistle to Titus 3:9 as a source for §4 of Isidore of Seville's De ecclesiasticis officiis 2.11, i.e. the chapter De lectoribus, which forms an important document in the history of linguistic education and the historical (socio)linguistics of early 7th-century Visigothic Spain. This source identification provides the basis for a suggestion of textual criticism and for two more general observations. This note identifies Jerome's commentary on Paul's Epistle to Titus 3:9 as a source for §4 of Isidore of Seville's De ecclesiasticis officiis 2.11, i.e. the chapter De lectoribus, which forms an important document in the history of linguistic education and the historical (socio)linguistics of early 7th-century Visigothic Spain. This source identification provides the basis for a suggestion of textual criticism and for two more general observations.