4 "The path of the just, as a shining light, goeth forwards and increaseth even to perfect day." (3) These words of Holy Scripture may well be applied to the life and activity of St. Leo. To be convinced of this we have but to consider St. Leo in his three main characteristic roles: 1) as a man singularly dedicated to the service of the Apostolic See, 2) as Christ's chief Vicar on earth, and 3) as Doctor of the universal Church.
Source: Aeterna Dei Sapientia (Vatican.va)