In his Latin preface to the First Series of Catholic Homilies, Ælfric lists six source authors: Augustine, Jerome, Bede, Gregory, Smaragdus and Haymo. The fact that Haymo is named in a phrase of his own at the end, ‘et aliquando Haymonem’, and is specified as being used ‘aliquando’, suggests that he was in some sense a supplementary source, as modern studies have tended to confirm. Smaragdus, by contrast, stands with Augustine, Jerome, Bede and Gregory as if Ælfric, in thinking back over the work he had done for the Catholic Homilies, had found Smaragdus as useful as the others and had consulted him about as frequently. Yet it is a puzzling fact that modern source studies have identified very little material drawn from Smaragdus's exegetical Expositio libri comitis. It is possible, of course, that Ælfric's claim to have used Smaragdus was unjustified, but although medieval writers often made false claims, Ælfric did not habitually do so; on the contrary, he was very conscious of his relationship to authoritative sources and, when he named an authority, his claims were usually as reliable as contemporary traditions allowed.