Cat. xviii. contains many indications from which we may conclude with certainty that it was delivered either on the night of Good Friday, or in the early hours of the morning of the “Great Sabbath.”  Thus in § 17 he speaks of “the weariness caused by the prolongation (ὑπερθέσεως) of the fast of the Preparation (Friday), and the watching.”  In § 21 he calls upon the Candidates to recite the Creed, which he had dictated to them, and which they would be required to repeat more publicly immediately before their Baptism, as we learn from § 32:  “Concerning the holy Apostolic Faith which has been delivered to you to profess (εἰς ἐπαγγελίαν), we have spoken through the grace of the Lord as many Lectures as was possible in these past days of Lent.…But now the holy day of the Passover is at hand, and ye, beloved in Christ, are to be enlightened by the washing of regeneration.  Ye shall therefore again be taught what is requisite if God so will; with how great devotion and order you must enter in when summoned, for what purpose each of the holy mysteries of Baptism is performed, and with what reverence and order you must go from Baptism to the holy altar of God, and enjoy its spiritual and heavenly mysteries.”  The additional instructions here promised were to be given on the same day as the last Lecture, Cat. xviii, that is on Easter Eve immediately before Baptism.  For it was forbidden to reveal the mysteries of Baptism, Chrism, and the Holy Eucharist to the uninitiated, and yet it was necessary that the Candidates should not come wholly unprepared to perform what would be required of them.  The full explanation of the various ceremonies and of the doctrines implied in them was reserved for the Mystagogic Lectures, which were to be delivered on Easter Monday and the four following days, after the public Service, not in the great Basilica, but in the Holy Sepulchre itself.