15 Among the virtues that priests must possess for their sacred ministry none is so important as a frame of mind and soul whereby they are always ready to know and do the will of him who sent them and not their own will. The divine task that they are called by the Holy Spirit to fulfill surpasses all human wisdom and human ability. "God chooses the weak things of the world to confound the strong" (1 Cor 1:27). Aware of his own weakness, the true minister of Christ works in humility trying to do what is pleasing to God. Filled with the Holy Spirit, he is guided by him who desires the salvation of all men. He understands this desire of God and follows it in the ordinary circumstances of his everyday life. With humble disposition he waits upon all whom God has sent him to serve in the work assigned to him and in the multiple experiences of his life. However, the priestly ministry, since it is the ministry of the Church itself, can only function in the hierarchical union of the whole body. Pastoral charity, therefore, urges priests, as they operate in the framework of this union, to dedicate their own will by obedience to the service of God and their fellow men. In a great spirit of faith, let them receive and execute whatever orders the holy father, their own bishop, or other superiors give or recommend. With a willing heart let them spend and even exhaust themselves in whatever task they are given, even though it be menial and unrecognized. They must preserve and strengthen a necessary oneness with their brothers in the ministry, especially with those whom God has selected as visible rulers of his Church. For in this way they are laboring to build the Body of Christ which grows "through every gesture of service." This obedience is designed to promote the mature freedom of the children of God; by its very nature it postulates that in the carrying out of their work, spurred on by charity, they develop new approaches and methods for the greater good of the Church. With enthusiasm and courage, let priests propose new projects and strive to satisfy the needs of their flocks. Of course, they must be ready to submit to the decisions of those who rule the Church of God. By this humility and by willing responsible obedience, priests conform themselves to Christ. They make their own the sentiments of Jesus Christ who "emptied himself, taking on the form of a servant," becoming obedient even to death (Phil 2:7-9). By this obedience he conquered and made up for the disobedience of Adam, as the Apostle testifies, "for as by the disobedience of one man, many were made sinners, so also by the obedience of one, many shall be made just"(Rom 5:19).
Source: Presbyterorum Ordinis (Vatican.va)