Nativitatis Dominicæ sacramento nobis clarius coruscante: cf. XXVI. chap. 1, note 1. I have no doubt that sacramentum here is almost equivalent to “the festival with its sacred observances” (cf. Bright’s n. 8), but I have preferred to translate it as uniformly as possible by the same word “mystery.” Cf. Sermon XXXI. chap. 1.