Offering on successive days of thirty Masses said for the same deceased person, to obtain the deliverance of that soul from purgatory, through the benevolent dispensation of God's mercy. The Church has declared that the confidence of the faithful in the special efficacy of the Gregorian Masses is pious and reasonable (Sacred Congregation for Indulgences, August 24, 1888). More than one series of Gregorian Masses may be offered, but not for more than one person at a time. Also the special fruits of these Masses apply only to the deceased. But the Masses need not be said by the same priest or at the same altar. Belief in the efficacy of the Gregorian Masses is based on a private revelation made to Pope St. Gregory I.