51 Moreover, the Church cannot and should not fail to realize that the choice of celibacy—provided that it is made with human and Christian prudence and responsibility—is governed by grace which, far from destroying or doing violences to nature, elevates it and imparts to it supernatural powers and vigor. God, who has created and redeemed man, knows what He can ask of him and gives him everything necessary to be able to do what his Creator and Redeemer asks of him. St. Augustine, who had fully and painfully experienced in himself the nature of man, exclaimed: "Grant what You command, and command what You will.'' (100)
Source: Sacerdotalis Caelibatus (Vatican.va)