44 Because Christ the Head holds such an eminent position, one must not think that he does not require the help of the Body. What Paul said of the human organism is to be applied likewise to the Mystical Body: "The head cannot say to the feet: I have no need of you." It is manifestly clear that the faithful need the help of the Divine Redeemer, for He has said: "Without me you can do nothing," and according to the teaching of the Apostle every advance of this Mystical Body towards its perfection derives from Christ the Head. Yet this, also, must be held, marvelous though it may seem: Christ has need of His members. First, because the person of Jesus Christ is represented by the Supreme Pontiff, who in turn must call on others to share much of his solicitude lest he be overwhelmed by the burden of his pastoral office, and must be helped daily by the prayers of the Church. Moreover as our Savior does not rule the Church directly in a visible manner, He wills to be helped by the members of His Body in carrying out the work of redemption. That is not because He is indigent and weak, but rather because He has so willed it for the greater glory of His spotless Spouse. Dying on the Cross He left to His Church the immense treasury of the Redemption, towards which she contributed nothing. But when those graces come to be distributed, not only does He share this work of sanctification with His Church, but He wills that in some way it be due to her action. This is a deep mystery, and an inexhaustible subject of meditation, that the salvation of many depends on the prayers and voluntary penances which the members of the Mystical Body of Jesus Christ offer for this intention and on the cooperation of pastors of souls and of the faithful, especially of fathers and mothers of families, a cooperation which they must offer to our Divine Savior as though they were His associates.
Source: Mystici Corporis Christi (Vatican.va)