10 As to the means to be employed in attaining this great end, it seems superfluous to name them, for they are obvious of themselves. Let your first care be to form Christ in those who are destined from the duty of their vocation to form Him in others. We speak of the priests, Venerable Brethren. For all who bear the seal of the priesthood must know that they have the same mission to the people in the midst of whom they live as that which Paul proclaimed that he received in these tender words: "My little children, of whom I am in labor again until Christ be formed in you" ( Gal . iv., 19). But how will they be able to perform this duty if they be not first clothed with Christ themselves? and so clothed with Christ as to be able to say with the Apostle: "I live, yet not I, but Christ lives in me" ( Ibid . ii., 20). "For me to live is Christ" ( Phlipp . i., 21). Hence although all are included in the exhortation "to advance towards the perfect man, in the measure of the age of the fullness of Christ" ( Ephes . iv., 3), it is addressed before all others to those who exercise the sacerdotal ministry; thus these are called another Christ, not merely by the communication of power but by reason of the imitation of His works, and they should therefore bear stamped upon themselves the image of Christ.
Source: E Supremi (Vatican.va)