Ex. xxxiii. 13.  Cyril means that even before His Incarnation Christ was seen as far as was possible by Prophets such as Moses.  This view was held by many of the Fathers before Cyril.  See Justin M. (Tryph. § 56 ff.); Tertull. (adv. Praxean, § 16); Euseb. (Demonstr. Evang. V. 13–16).